Amorphous iron-based silicon phosphorus composite negative electrode material and preparation method and application thereof

Abstract

The invention discloses an amorphous iron-based silicon-phosphorus composite negative electrode material and a preparation method and application thereof, the raw materials of the iron-based silicon-phosphorus composite negative electrode material comprise an iron element, a silicon element, a phosphorus element and a carbon material, the molar ratio of the silicon element to the phosphorus element is 2: 1-1: 2, the molar ratio of the silicon element to the iron element is 8: 1-1: 2, and the mass ratio of an iron / silicon / phosphorus mixture to the carbon material is 5: 5-8: 2; the iron-based silicon phosphorus composite negative electrode material is prepared by a one-step or multi-step mechanical ball milling method. In the iron-based silicon phosphorus composite negative electrode material, the introduction of the iron elementary substance induces the microstructure to be disordered and reduces the lithium ion diffusion energy barrier, and meanwhile, the iron elementary substance and the lithium phosphide formed in situ respectively provide abundant electron and ion transmission paths and cooperatively buffer the huge volume deformation of the silicon negative electrode in the lithiation / delithiation process; furthermore, the electrochemical reversibility, the cycling stability and the rate capability of the material in the lithium storage process are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery anode material technology, specifically to an amorphous iron-based silicon-phosphorus composite anode material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries possess advantages such as high energy density, long cycle life, no memory effect, and mature manufacturing processes, leading to their widespread application in portable consumer electronics and continuously driving the rapid development of the electric vehicle and large-scale energy storage industries. However, current commercial lithium-ion batteries are limited by the finite specific capacity and operating voltage of traditional electrode materials, resulting in energy density reaching its limit and poor rate performance. This makes it difficult to meet the practical demands of long driving range and fast charging for electric vehicles. Therefore, we urgently need to improve the fundamental electrochemical performance of lithium-ion batteries by updating the electrode material system.

[0003] As a commercial lithium-ion battery anode material, graphite has a low and stable operating voltage, but its theoretical capacity is only 372 mAh g⁻¹. -1 This makes it difficult to meet the design requirements of high-energy-density lithium-ion batteries. Silicon, on the other hand, is abundant and inexpensive, and can be combined with Li at lower potentials. + Silicon undergoes reversible alloying / dealloying reactions involving multiple electrons, resulting in extremely high theoretical capacity, low operating voltage, and ultra-high energy density. It is considered a key anode material for next-generation lithium-ion batteries. However, silicon's poor structural stability and poor electronic / ionic conductivity during discharge / charge significantly reduce its electrochemical performance. First, the massive volume expansion / contraction (~400%) of the silicon anode material itself during lithiation / delithiation directly leads to structural collapse, electrode pulverization, and rapid decay of reversible capacity and operating voltage. Second, the large volume change not only directly damages the solid electrolyte interface layer of the silicon anode, reducing electrode structural stability, but also accelerates interfacial side reactions between freshly exposed silicon particles and the active electrolyte, promoting the disordered growth of an uneven solid electrolyte interface layer and severely depleting the available active Li- in the lithium-ion battery. + This significantly reduces its coulombic efficiency and cycle life. Even worse, silicon itself has poor electronic conductivity (10⁻⁶ Ω·cm). -5 ~10 -3 S cm -1 ) and ionic conductivity (10 -14 ~10 -13 cm 2 s -1 This will severely hinder the electrochemical reaction process of Li + The rapid migration of electrons in the active material leads to large electrochemical polarization and poor rate performance under high current.

[0004] In mainstream silicon anode research, carbon composites can mitigate structural instability and sluggish reaction kinetics during lithium storage. However, conventional chemical vapor deposition (CVD) and mechanical ball milling methods result in a high proportion of low-electrochemically active carbon materials in silicon / carbon anode materials, directly weakening the overall reversible capacity and energy density. Furthermore, the poor lithium-ion conductivity of carbon materials further limits the lithium storage reaction kinetics and rate performance of silicon / carbon anode materials. Meanwhile, the reported synthesis processes for porous silicon / carbon anode materials are complex and costly, hindering industrial application.

[0005] Phosphorus, as a typical alloy anode material, is not only abundant and inexpensive, but also compatible with multiple Li-type lithium oxides. + It undergoes a reversible alloying / dealloying reaction and has an extremely high theoretical specific capacity (2596 mAh g). -1 Phosphorus has excellent rate performance and outstanding volumetric energy density. Although phosphorus has a higher lithium storage potential (>0.7 V vs. Li / Li), it also exhibits superior performance. + This will inevitably reduce its energy density, but in practical full cells, the safe operating voltage of the negative electrode (>0 V vs. Li / Li) is... + This will effectively prevent the precipitation of lithium dendrites on the negative electrode under high-rate charging, improving the safety of lithium-ion batteries under operating conditions. At the same time, phosphorus has a relatively low solid-phase lithium-ion diffusion barrier and can spontaneously form high lithium-ion conductivity (~10). -4 S cm -1 Lithium phosphide (Li3P) exhibits excellent fast-charging performance due to its low desolvation energy. In summary, introducing phosphorus into silicon / carbon anodes effectively improves their electrochemical activity, cycle reversibility, and rate performance. However, phosphorus itself has relatively poor electronic conductivity (~10⁻⁶). -14 S cm -1 The large volume change (~300%) during lithium storage limits its widespread application in silicon / carbon anodes. Therefore, constructing silicon-phosphorus composite anode materials with high conductivity and high stability is of great research significance and commercial value for developing high-capacity and long-life lithium-ion batteries.

[0006] Chinese patent CN202510911101.2 discloses a method for preparing a phosphorus / silicon composite anode material. The main steps are as follows: on a porous carbon substrate, silane is first deposited at 600-800℃ to form a silicon layer; then, the temperature is lowered to 300-500℃ to introduce a phosphorus source, allowing it to permeate into the 2-50 nm mesopores; finally, the substrate is held at 260-350℃ for 24-72 hours to convert elemental phosphorus into amorphous red phosphorus nanoparticles. This method sequentially deposits silicon and phosphorus in the porous carbon channels, utilizing the spatial confinement effect of the porous carbon to suppress volume expansion, and leverages the high lithiation potential and high specific capacity of phosphorus to improve the material's cycle stability and specific capacity. However, the process involves multiple steps, long-cycle high and low temperature cycling, and gas switching, resulting in high energy consumption and low efficiency, which is not conducive to industrial mass production.

[0007] Chinese patent CN202411419132.8 discloses a method for preparing a phosphorus-silicon co-doped silicon-carbon composite anode material. This method first involves vapor deposition of phosphorus source gas through porous carbon, followed by the introduction of a mixed gas of phosphorus and silicon sources (with the phosphorus source ratio gradually decreasing), and finally, the introduction of a hydrocarbon gas for carbon coating. This method aims to improve the lithium-ion transport kinetics at the silicon-carbon interface, buffer volume expansion, and enhance the material's rate capability and cycle performance by forming a layered inner shell structure with phosphorus and silicon elements. However, the process employs a fluidized bed and involves complex multi-stage gas introduction and ratio control, requiring extremely high equipment precision and process control, thus increasing the difficulty and cost of mass production.

[0008] Chinese patent CN202010345495.7 discloses a phosphorus-doped silicon-based anode material and its preparation method. This method involves mixing a phosphorus-doped material with silicon-based powder, followed by chemical vapor deposition in a high-temperature rotary kiln at 800-1000℃ under an argon atmosphere. This allows phosphorus to partially diffuse and form substitutional dopant, while partially interacting with a carbon layer, ultimately yielding a phosphorus-doped silicon-based composite anode material. However, the high-temperature rotary kiln process is energy-intensive, and the coupling of the carbon layer deposition and phosphorus doping processes makes process control complex, affecting batch-to-batch consistency. Furthermore, this preparation method involves multiphase diffusion and reaction of phosphorus at high temperatures, making precise process control difficult and potentially leading to localized compositional inhomogeneities in the material, thus affecting overall electrochemical performance. Summary of the Invention

[0009] To address the aforementioned problems in the prior art, this invention provides an amorphous iron-based silicon-phosphorus composite anode material, its preparation method, and its applications, which can significantly improve the specific capacity, high-rate performance, and long cycle life of lithium batteries. This invention directly converts mechanical energy into chemical energy through high-speed ball milling, promoting the uniform nanoscale composite of iron, silicon, phosphorus, and carbon, effectively disrupting the ordered structure of silicon / phosphorus elements, increasing the structural disorder of the silicon-phosphorus composite material, and reducing the ion diffusion barrier in the isotropic microstructure. Furthermore, by constructing continuous and abundant electron and ion transport pathways through elemental iron and in-situ formed lithium phosphide, and synergistically buffering the large volume deformation of the silicon anode during lithiation / delithiation, it effectively improves the electrochemical reversibility, cycle stability, and rate performance during lithium storage. The prepared iron-based silicon-phosphorus anode, after appropriate pre-lithiation, can be combined with commercial cathode materials to assemble high-energy-density, high-rate-performance, and long-cycle-life lithium-ion full batteries.

[0010] The objective of this invention is achieved through the following technical solution: an amorphous iron-based silicon-phosphorus composite anode material, the raw materials of which include elemental iron, elemental silicon, elemental phosphorus and carbon materials, wherein the molar ratio of silicon to phosphorus is 2:1 to 1:2, the molar ratio of silicon to iron is 8:1 to 1:2, and the mass ratio of the mixture of elemental iron, elemental silicon and phosphorus to carbon materials is 5:5 to 8:2; the iron-based silicon-phosphorus composite anode material is prepared by one-step or multi-step mechanical ball milling.

[0011] Specifically, the source of the iron element is elemental iron powder or nano-iron powder; the source of the silicon element is elemental silicon powder or nano-silicon powder; the source of the phosphorus element is elemental phosphorus powder or nano-phosphorus powder; and the carbon material is conductive carbon black or carbon nanomaterial.

[0012] Furthermore, the mass ratio of the mixture of silicon, phosphorus, and iron to carbon material is 5:5, 6:4, 7:3, or 8:2; the purity of silicon is 99.9% and the particle size is 50-500 nm; the purity of phosphorus is 98-99.99%.

[0013] To address the aforementioned technical problems, the present invention also provides another technical solution: a method for preparing the amorphous iron-based silicon-phosphorus composite negative electrode material, comprising the following steps: (1) Weigh out elemental silicon, elemental phosphorus, elemental iron, and carbon materials; (2) Weigh the grinding balls; (3) The iron-based silicon-phosphorus composite anode material is prepared by one or more steps of mechanical ball milling.

[0014] Specifically, the one-step mechanical ball milling method in step (3) is as follows: First, the raw materials weighed in step (1) and the grinding balls weighed in step (2) are transferred to a ball milling jar; then, in argon gas, the ball milling jar is assembled, and the iron, silicon, phosphorus and carbon materials in step (1) are mixed and ground using a ball mill. First, preliminary physical mixing is carried out at speeds of 100~200 rpm and 200~300 rpm for 8~24 h respectively, followed by high-energy ball milling at speeds of 300~600 rpm for 12~48 h; the preliminary physical mixing and high-energy ball milling are repeated at least twice to obtain the material.

[0015] Specifically, the multi-step mechanical ball milling method in step (3) is as follows: First, the iron, silicon, and phosphorus elements weighed in step (1) and the grinding balls weighed in step (2) are transferred to a ball milling jar and assembled in an argon atmosphere. Then, gradient ball milling technology is used to first perform preliminary physical mixing at speeds of 100-200 rpm and 200-300 rpm for 8-24 h, respectively. Then, high-energy ball milling is performed at speeds of 300-600 rpm for 12-48 h. The above preliminary physical mixing and high-energy ball milling are repeated at least twice to obtain the iron-silicon-phosphorus anode material. Then, the carbon material weighed in step (1) and the prepared iron-silicon-phosphorus anode material are added to a ball mill jar and sealed and assembled in an argon atmosphere. Finally, gradient ball milling technology is used to first perform preliminary physical mixing at speeds of 100~200 rpm and 200~300 rpm for 8~24 h, and then perform high-energy ball milling at speeds of 300~600 rpm for 12~48 h. The above preliminary physical mixing and high-energy ball milling are repeated at least twice to obtain an amorphous iron-based silicon-phosphorus composite anode material.

[0016] Preferably, the raw material to mass ratio of the grinding balls is 20:1 to 50:1; the grinding balls are made of stainless steel beads of different sizes with diameters of 2 to 10 mm; the protective atmosphere is one or more of argon, nitrogen, helium, argon and hydrogen, or a mixture of nitrogen and hydrogen; in the process of high-energy ball milling at 100 to 200 rpm for 8 to 24 hours, high-energy ball milling at 100, 150, or 200 rpm for 12 to 18 hours is selected; in the process of high-energy ball milling at 200 to 300 rpm for 8 to 24 hours, high-energy ball milling at 200, 250, or 300 rpm for 12 to 18 hours is selected; in the process of high-energy ball milling at 300 to 600 rpm for 12 to 48 hours, high-energy ball milling at 350, 400, 450, or 500 rpm for 24 to 36 hours is selected.

[0017] Furthermore, the mass ratio of the grinding balls to the raw materials is 20:1, 30:1, or 40:1; three types of stainless steel balls with sizes of 2mm, 3mm, and 5mm are selected and mixed, and the mass ratio of the three types of stainless steel balls is 1:1:1.

[0018] To address the aforementioned technical problems, this invention also provides another technical solution: a lithium-ion half-cell, the preparation method of which includes the following steps: S1. The iron-based silicon-phosphorus composite material, conductive carbon black, and binder are weighed at a mass ratio of m:n:l to obtain a mixture, wherein m is 60~80 wt.%, n is 10~30 wt.%, and l is 10~30 wt.%. The mixture is uniformly dispersed in deionized water to prepare an electrode slurry. S2. The slurry obtained in step S1 is uniformly coated onto copper foil and vacuum dried at 60~70 ℃ for 10~15 hours. Then the copper foil is cut into circular electrode sheets for later use. S3. Using the electrode obtained in step S2 as the negative electrode and the lithium metal sheet as the counter electrode, an electrolyte is added and the cells are assembled into a half-cell. The electrolyte is 1.0 M LiPF6 in DMC:EC:EMC = 1:1:1 Vol% with 10% FEC and 2% VC.

[0019] To address the aforementioned technical problems, this invention also provides another technical solution: a lithium-ion full battery, the preparation method of which includes the following steps: S'1. Weigh the iron-based silicon-phosphorus composite material, conductive carbon black, and binder in a mass ratio of m:n:l, where m is 60~80 wt.%, n is 10~30 wt.%, and l is 10~30 wt.%. Disperse the mixture uniformly in deionized water to prepare an electrode slurry. S'2. The slurry obtained in step S'1 is uniformly coated onto copper foil and vacuum dried at 60~70 ℃ for 10~15 hours. Then the copper foil is cut into circular electrode sheets for later use. S'3. Weigh the positive electrode active material, conductive carbon black, and binder according to the mass ratio of m:n:l, where m is 60~80 wt.%, n is 10~30 wt.%, and l is 10~30 wt.%. Disperse the mixture uniformly in N-methylpyrrolidone solvent to prepare the electrode slurry. S'4. The slurry obtained in step S'3 is uniformly coated onto aluminum foil, dried at 90~120 ℃ for 10~15 hours, and then the aluminum foil is cut into circular electrode sheets for later use. S'5. Physically pre-lithiate the electrode obtained in step S'2. The physical pre-lithiation involves physically bonding the negative electrode with lithium metal in an appropriate amount of electrolyte while applying an external pressure of 0.2~1.0 MPa for 10~30 minutes. S'6. Using the electrode obtained in step S'5 as the negative electrode and the electrode obtained in step S'4 as the counter electrode, add electrolyte and assemble into a full cell. The electrolyte is 1.0 M LiPF6 in EC:DMC:EMC = 3:4:3 Vol% with 10% FEC and 2% VC, or 1.0 M LiPF6 in DMC:EC:EMC = 1:1:1 Vol% with 10% FEC and 2% VC, or 1.0 M LiPF6 in EC:EMC = 3:7 Vol% with 5% FEC, 2% VC, and 3% TEOSCN, or 1.0 M LiPF6 in EC:DMC:EMC = 1:1:1 Vol% with 10% FEC and 1-2% MBA, or 1.2 M LiFSI with 0.05 M LiDFOB in DME:HFE:FEC = 3:6:1 Vol%.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects: 1. This invention reduces the crystallinity of the material by introducing Fe, inducing structural disorder, promoting grain boundary fusion, accelerating ion diffusion, and mitigating internal stress through isotropic volume changes. During ball milling, driven by high-energy mechanical force, mechanochemical reactions occur between the components, in-situ constructing an integrated composite structure with nano-iron as conductive nodes, phosphorus / silicon as a high-capacity active core, and carbon as a buffer and continuous conductive framework. This structure spontaneously forms and remains stable during the preparation process, achieving an intrinsic unity of conductivity, capacity, and structural stability.

[0021] 2. The introduction of an appropriate amount of Fe element in this invention can enhance the Fe-P bond, thereby promoting the charge transfer process. Furthermore, the high-speed ball milling technology, which is simple, inexpensive, and easy to scale up, completes the preparation of the final composite anode material from the raw powder in a single ball milling step. This process eliminates the need for complex high-temperature vapor deposition, wet chemical synthesis, or subsequent coating treatments; the process is concise, requires less equipment, significantly reduces energy consumption, and is easy to scale up for production. This efficient and low-cost solid-state process breaks through the limitations of high-performance anode material preparation, which typically relies on complex and expensive technologies, and has outstanding potential for industrial application.

[0022] 3. The anode material prepared by this invention successfully solves the key technical challenge of simultaneously achieving high capacity, high rate capability, and long cycle life. Specifically, it exhibits: high capacity (based on the high theoretical capacity of silicon and phosphorus); high rate capability (benefiting from the high-speed electron / ion three-dimensional conduction network constructed from iron and carbon); and high cycle stability (the carbon matrix and iron network effectively buffer the significant volume expansion of silicon / phosphorus during cycling and maintain the integrity of the electrode structure). This invention achieves a simultaneous and significant improvement in these typically mutually restrictive performance indicators within a single material system.

[0023] 4. During the ball milling process, the negative electrode material prepared by this invention forms a stable interface through close contact and potential chemical bonding between the active components (silicon, phosphorus) and conductive carbon and metallic iron. This stable interface effectively reduces the direct contact between the active material and the electrolyte during charging and discharging, thereby significantly suppressing harmful side reactions and the uncontrolled growth of the solid electrolyte interphase (SEI) film, achieving high initial coulombic efficiency and long cycle life.

[0024] 5. This invention forms a highly conductive and stable compound framework (FeP). x Its conductivity mechanism is superior to that of pure iron nanoparticles; it acts as a "chemical anchor" to enhance interfacial bonding (chemical bonding vs. physical contact); and it actively coordinates volume expansion through phase transition (FeP). x (The controllable volume change is coordinated with the expansion of Si); and it synergistically constructs an "electron-ion" dual conductive interface with phosphorus. The iron of this invention is an active, reactive "structural functional unit" with synergistic and nonlinear effects, producing a "1+1>2" technical effect. Attached Figure Description

[0025] Figure 1 The XRD patterns are of the composite materials prepared by Examples 4, 5, 6 and Comparative Example 1.

[0026] Figure 2 The XPS full spectrum of the composite materials prepared by Examples 4, 5, 6 and Comparative Example 1 is shown.

[0027] Figure 3 The Fe 2p XPS spectra of the composite materials prepared by Examples 4, 5, 6 and Comparative Example 1 are shown.

[0028] Figure 4 The P 2p XPS spectra of the composite materials prepared in Examples 4, 5, 6 and Comparative Example 1 are shown.

[0029] Figure 5 The Si 2p XPS spectra of the composite materials prepared in Examples 4, 5, 6 and Comparative Example 1 are shown.

[0030] Figure 6 The Raman spectra of the composite materials prepared in Examples 4, 5, 6 and Comparative Example 1 are shown.

[0031] Figure 7 The composite materials prepared in Examples 4, 5, 6 and Comparative Example 1 were subjected to a concentration of 0.5 A g. -1 Cyclic performance at current density.

[0032] Figure 8 The composite materials prepared in Examples 4, 5, 6 and Comparative Example 1 were subjected to a reaction at 1 A g. -1 Cyclic performance at current density.

[0033] Figure 9 The composite materials prepared in Examples 4, 5, 6 and Comparative Example 1 were subjected to a reaction at 2 A g. -1 Cyclic performance at current density.

[0034] Figure 10 The composite materials prepared in Examples 4, 5, 6 and Comparative Example 1 were subjected to a reaction at 5 A g. -1 Cyclic performance at current density.

[0035] Figure 11 The composite materials prepared in Examples 4, 5, 6 and Comparative Example 1 were subjected to a reaction at 10 A g. -1 Cyclic performance at current density.

[0036] Figure 12 The charge-discharge curves of the composite material prepared in Comparative Example 1 at different current densities are shown.

[0037] Figure 13 The graphs show the charge-discharge curves of the composite material prepared in Example 5 at different current densities.

[0038] Figure 14 The graphs show the rate performance of the composite materials prepared in Examples 4, 5, 6 and Comparative Example 1 at different current densities.

[0039] Figure 15 The composite material prepared in Example 4 was at 0.2 mV s -1 CV graph at scan speed.

[0040] Figure 16 The composite material prepared in Example 5 was at 0.2 mV s -1 CV graph at scan speed.

[0041] Figure 17 The composite material prepared in Example 6 was at 0.2 mV s -1CV graph at scan speed.

[0042] Figure 18 The composite material prepared for Comparative Example 1 was tested at 0.2 mV s. -1 CV graph at scan speed.

[0043] Figure 19 The CV curves of the composite material prepared in Example 5 at different scan rates are shown.

[0044] Figure 20 The CV curves of the composite material prepared in Comparative Example 1 at different scan rates are shown.

[0045] Figure 21 The graph shows the linear fit between the peak current and the square root of the scan rate in the CV test of the composite materials prepared in Example 5 and Comparative Example 1.

[0046] Figure 22 This is a SEM image of the composite material prepared in Example 5.

[0047] Figure 23 The full cell assembled from the composite material prepared in Example 5 was tested at 0.1 A g. -1 Cyclic performance at current density.

[0048] Figure 24 The full cell assembled from the composite material prepared in Example 5 was tested at 0.2 A g. -1 Cyclic performance at current density.

[0049] Figure 25 The full cell assembled from the composite material prepared in Example 5 was tested at 0.1 A g. -1 Charge-discharge curves at current density.

[0050] Figure 26 The full cell assembled from the composite material prepared in Example 5 was tested at 0.2 A g. -1 Charge-discharge curves at current density.

[0051] Figure 27 The graph shows the rate performance of the full cell assembled from the composite material prepared in Example 5 at different current densities.

[0052] Figure 28 The graphs show the charge-discharge curves of the full battery assembled from the composite material prepared in Example 5 at different current densities. Detailed Implementation

[0053] The iron-based silicon-phosphorus composite anode material of the present invention is obtained by the following preparation method, which includes the following steps: (1) Weigh out elemental iron, elemental silicon, elemental phosphorus, and carbon materials; (2) Weigh the grinding balls; (3) Iron-based silicon-phosphorus composite anode materials are prepared by one-step or multi-step mechanical ball milling.

[0054] The iron is sourced from elemental iron powder or nano-iron powder; the silicon is sourced from elemental silicon powder or nano-silicon powder; the phosphorus is sourced from elemental phosphorus powder or nano-phosphorus powder; and the carbon material is conductive carbon black or carbon nanomaterial.

[0055] It should be noted that the elemental silicon powder, elemental phosphorus powder, and elemental iron powder mentioned in this invention refer to particles with a particle size typically in the micrometer range, usually irregular or spherical, visible under a microscope, and with a low specific surface area, typically <1 μm. 2 / g has low chemical activity. It oxidizes slowly (rusts) in air, with a slow reaction rate. It is low in cost and used in large quantities, based on the bulk properties of iron. In contrast, nano-silicon powder, nano-phosphorus powder, and nano-iron powder typically have particle sizes at the nanoscale, mostly in the form of spherical or chain-like aggregates (due to high surface energy). They are invisible to the naked eye and under ordinary microscopes, appearing as loose powders; they have high specific surface area, strong performance, and high efficiency, based on their surface and nanoscale properties (such as high specific surface activity and superparamagnetism), and their cost is higher than that of elemental silicon powder, elemental phosphorus powder, and elemental iron powder.

[0056] The silicon has a purity of 99.9% and a particle size of 50-500 nm; the phosphorus has a purity of 98-99.99%.

[0057] The molar ratio of silicon to phosphorus is 2:1 to 1:2, and the molar ratio of silicon to iron is 8:1 to 1:2.

[0058] The mass ratio of the mixture of elemental silicon, elemental phosphorus and elemental iron to carbon material is 5:5-8:2, preferably 5:5, 6:4, 7:3 or 8:2.

[0059] The mass ratio of the total amount of grinding balls in step (2) to the total amount of raw materials in step (1) is 20:1 to 50:1, preferably 20:1, 30:1 or 40:1.

[0060] The grinding ball is composed of three different sizes of stainless steel beads with diameters of 2 to 10 mm. Preferably, three stainless steel beads with sizes of 2 mm, 3 mm and 5 mm are selected and mixed together, and the mass ratio of the three stainless steel balls is 1:1:1.

[0061] The one-step mechanical ball milling method in step (3) is as follows: First, the raw materials weighed in step (1) and the grinding balls weighed in step (2) are transferred to a stainless steel ball milling jar; then, in a glove box with a high-purity argon atmosphere, a sealed ball milling jar with a stainless steel liner is assembled, and a planetary ball mill is used to mix and grind the iron, silicon, phosphorus and carbon materials in step (1). Gradient ball milling technology is used, and the initial physical mixing is carried out at speeds of 100~200 rpm and 200~300 rpm for 8~24 h respectively. Then, high-energy ball milling is carried out at speeds of 300~600 rpm for 12~48 h. The above ball milling steps are repeated at least twice to achieve uniform composite of iron, silicon, phosphorus and carbon elements at the nanoscale, thereby preparing iron-based silicon-phosphorus composite anode materials with uniform particle size and uniform dispersion.

[0062] The multi-step mechanical ball milling method in step (3) is as follows: First, the iron, silicon, and phosphorus elements weighed in step (1) and the grinding balls weighed in step (2) are transferred to a stainless steel ball milling jar and sealed and assembled in a glove box under an argon atmosphere. Then, gradient ball milling technology is used to first perform preliminary physical mixing at speeds of 100~200 rpm and 200~300 rpm for 8~24 h respectively, followed by high-energy ball milling at speeds of 300~600 rpm for 12~48 h, and the above ball milling steps are repeated at least twice to achieve uniform composite of silicon, phosphorus and iron at the nanoscale, thereby obtaining the original silicon-phosphorus anode material. Then, the carbon material weighed in step (1) and the prepared iron-silicon-phosphorus anode material are added together into a stainless steel ball mill jar and sealed and assembled in an argon atmosphere glove box. Finally, gradient ball milling technology is used to first perform preliminary physical mixing at speeds of 100~200 rpm and 200~300 rpm for 8~24 h respectively, followed by high-energy ball milling at speeds of 300~600 rpm for 12~48 h, and the above ball milling steps are repeated at least twice to achieve uniform composite of iron, silicon, phosphorus and carbon elements at the nanoscale, thereby obtaining iron-based silicon-phosphorus composite anode material with uniform particle size and uniform dispersion.

[0063] In the process of high-energy ball milling at 100-200 rpm for 8-24 hours, it is preferable to ball mill at 100, 150 or 200 rpm for 12-18 hours.

[0064] In the process of high-energy ball milling at 200-300 rpm for 8-24 hours, it is preferable to ball mill at 200, 250 or 300 rpm for 12-18 hours.

[0065] In the process of high-energy ball milling at 300-600 rpm for 12-48 h, it is preferred to ball mill at 350, 400, 450 or 500 rpm for 24-36 h.

[0066] The protective atmosphere is argon, nitrogen, helium, a mixture of argon and hydrogen, or a mixture of nitrogen and hydrogen.

[0067] The iron-based silicon-phosphorus composite lithium-ion battery anode material of the present invention has an initial charge specific capacity of 1090-1852 mAh g. -1 At 0.5 Ag -1 The specific capacity retention rate after 50-100 cycles at current density is 78-89%.

[0068] This invention also provides a lithium-ion half-cell, comprising a positive electrode shell, an iron-based silicon-phosphorus negative electrode, a composite separator, lithium metal, a gasket, a spring, a negative electrode shell, and an electrolyte. The preparation method of this lithium-ion half-cell includes the following steps: S1. The iron-based silicon-phosphorus composite material of the present invention is weighed with conductive carbon black (acetylene black, Super-P or Ketjen black) and binder (sodium hydroxymethyl cellulose, sodium alginate or polyacrylic acid / polyacrylonitrile) at a mass ratio of m:n:l, wherein m is 60~80 wt.%, n is 10~30 wt.%, l is 10~30 wt.%, and the mixture is uniformly dispersed in an appropriate amount of deionized water using a high-speed stirring degassing machine, thereby preparing an electrode slurry with stable properties and uniform dispersion. S2. The slurry obtained in step S1 is uniformly coated onto a clean copper foil, vacuum dried at 60~70 ℃ for 10~15 hours, and then cut into circular electrode sheets of the required size for later use. S3. Use the electrode obtained in step S2 as the negative electrode, which is the iron-based silicon-phosphorus negative electrode, and the lithium metal sheet as the counter electrode. After adding electrolyte, assemble it into a half cell. The electrolyte is 1.0 M LiPF6 in DMC:EC:EMC = 1:1:1 Vol% with 10% FEC and 2% VC.

[0069] Specifically, the electrolyte comprises a 1 mol / L LiPF6 electrolyte and a solution of ethylene carbonate (EC) / dimethyl carbonate (DMC) / ethyl methyl carbonate (EMC) (volume ratio 1:1:1) with 10 vol.% fluoroethylene carbonate (FEC) and 2 vol.% ethylene carbonate (VC) added.

[0070] The lithium-ion battery also includes a separator, which is composed of a 14-16 mm polymer membrane and is a PP / PE / PP composite membrane.

[0071] The lithium-ion half-cell prepared by the above method is a CR2032 button cell. The assembled battery was subjected to a 0.5 A g... -1 After 300 cycles at a current density, its initial charge specific capacity and the charge specific capacity after 300 cycles were tested. The initial charge specific capacity reached 1850.34 mAh g. -1 After 300 cycles, it still retains no less than 89% of its specific capacity.

[0072] This invention also provides a lithium-ion full battery, the preparation method of which includes the following steps: S'1. The iron-based silicon-phosphorus composite material of the present invention is weighed with conductive carbon black (acetylene black, Super-P or Ketjen black) and binder (sodium hydroxymethyl cellulose, sodium alginate or polyacrylic acid / polyacrylonitrile) at a mass ratio of m:n:l, wherein m is 60~80 wt.%, n is 10~30 wt.%, l is 10~30 wt.%, and the mixture is uniformly dispersed in an appropriate amount of deionized water using a high-speed stirring degassing machine, thereby preparing an electrode slurry with stable properties and uniform dispersion; S'2. Coat the slurry obtained in step S'1 evenly onto copper foil, vacuum dry it at 60~70 ℃ for 10~15 hours, and then cut it into circular electrode sheets for later use; S'3. Weigh the positive electrode active material (lithium-rich manganese-based positive electrode material, high-nickel layered oxide material, lithium nickel manganese oxide material or lithium iron phosphate material) with conductive carbon black (acetylene black, Super-P or Ketjen black) and binder (polyvinylidene fluoride) at a mass ratio of m:n:l, where m is 60~80 wt.%, n is 10~30 wt.%, and l is 10~30 wt.%. Use a high-speed stirrer to uniformly disperse the mixture in an appropriate amount of N-methylpyrrolidone solvent to prepare a stable and uniformly dispersed electrode slurry. S'4. The slurry obtained in step S'3 above is uniformly coated on aluminum foil, dried at 90~120 ℃ for 10~15 hours, and then cut into circular electrode sheets for later use; S'5. Physically pre-lithiate the electrode obtained in step S'2, that is, physically bond the negative electrode to lithium metal in an appropriate amount of electrolyte, while applying an external pressure of 0.2~1.0 MPa, and the pre-lithiation time is 10~30 minutes. S'6. Using the electrode obtained in step S'5 as the negative electrode and the electrode obtained in step S'4 as the counter electrode, add electrolyte and assemble into a full cell. The electrolyte is 1.0 M LiPF6 in EC:DMC:EMC = 3:4:3 (vol%) with 10% FEC and 2% VC. Alternatively, the electrolyte could be 1.0 M LiPF6 in DMC:EC:EMC = 1:1:1 (vol%) with 10% FEC and 2% VC. Alternatively, the electrolyte could be 1.0 M LiPF6 in EC:EMC = 3:7 (vol%) with 5% FEC, 2% VC, and 3% TEOSCN. Alternatively, the electrolyte can be 1.0 M LiPF6 in EC:DMC:EMC = 1:1:1 (vol%) with 10% FEC and 1-2% MBA. Alternatively, the electrolyte could be 1.2 M LiFSI with 0.05 M LiDFOB in DME:HFE:FEC = 3:6:1 Vol%.

[0073] The lithium-ion full battery also includes a separator, which is composed of a 14-16 mm polymer membrane and is a PP / PE / PP composite membrane.

[0074] The lithium-ion full battery prepared by the above method is a CR2032 button cell.

[0075] The present invention preferably uses a molar ratio of silicon to phosphorus of 2:1 to 1:2, a molar ratio of silicon to iron of 8:1 to 1:2, and a mass ratio of the mixture of elemental silicon, elemental phosphorus, and elemental iron to carbon material of 5:5-8:2, for the following reasons: I. Structural Principle: The goal is to construct an integrated nanocomposite architecture that combines confinement, conductivity, and buffering.

[0076] 1. Silicon-rich active core: Ultra-high capacity nano-silicon phase serves as the core for energy storage.

[0077] 2. In-situ generated phosphide interface layer and buffer network: iron phosphide (FeP) formed by the reaction of Fe and P. x ), and some SiP silicon phosphides formed by Si and P (SiP x Together, they form an intermediate layer that combines high conductivity and good plasticity.

[0078] 3. Continuous carbon encapsulation network: Carbon materials form a three-dimensional continuous coating layer.

[0079] 4. The choice of the silicon-to-phosphorus ratio (Si:P = 2:1 ~ 1:2) is to regulate the interplay between the "active core" and the "interfacial buffer layer." When Si is predominant (e.g., 2:1), the system mainly forms silicon-rich silicon-phosphorus compounds (such as SiP or solid solutions), while also containing a significant amount of free nano-silicon phase. This structure maximizes capacity because the high-capacity silicon phase dominates. However, the buffer layer (phosphide) is relatively thin, limiting its constraint on silicon expansion. At this point, the high capacity potential is greatest, but the requirements for subsequent carbon coating networks and electrode engineering are higher to compensate for the relative insufficiency of the buffer layer. When P is predominant (e.g., 1:2), the system tends to generate phosphorus-rich phosphides (such as SiP2, and possibly FeP2 with Fe), forming a thicker and more complete interfacial buffer layer. This greatly enhances the mechanical stability of the material and its interfacial stability with the electrolyte, providing a solid foundation for long cycle life. However, an excessively thick inactive or low-capacity phosphide layer can hinder lithium-ion diffusion into the internal silicon and dilute the overall capacity. At this point, the cycle stability potential is optimal, but some compromises must be made in rate capability and capacity. This range defines the optimal balance between capacity contribution (from Si) and interface stability / buffering capability (from phosphides). Adjustments within this range allow for material "fine-tuning" to suit different application priorities (whether energy density or cycle life is prioritized).

[0080] 5. Silicon-to-Fe ratio (Si:Fe = 8:1 1:2): Regulates the density and morphology of the "conductive network framework". When the Fe content is extremely low (Si:Fe = 8:1): Iron exists as a "catalytic seed" and "structure inducer". Its main function is to promote the formation of uniform phosphides and disperse as highly conductive nanodots in the matrix, providing efficient electron penetration pathways without significantly increasing inert mass. This is beneficial for improving rate performance while maintaining extremely high specific capacity. When the Fe content increases (Si:Fe shifts towards 1:2): Iron's role changes from "seed" to "framework builder". More iron reacts with phosphorus to form continuous or semi-continuous iron phosphides (FeP). x The composite material uses a carbon network. This network itself possesses excellent metallic conductivity and good toughness, enabling it to construct a robust secondary conductive and mechanical support framework, complementing the carbon network. This significantly enhances the overall structural integrity and electronic conductivity of the composite material, particularly beneficial for ultra-high rate charge / discharge and resistance to stress accumulation during long-term cycling, but at the cost of sacrificing some specific capacity by weight. The most economical Fe content can be selected within this range based on different levels of requirement for rate performance and mechanical strength.

[0081] 6. Active material to carbon ratio ((Fe+Si+P):C = 5:5 ~ 8:2): This balances "global conductive encapsulation" with "energy density." High carbon content (5:5): This means up to 50% carbon. This creates an extremely well-developed and robust 3D continuous conductive network and forms a very dense coating. The technical benefits are: maximized electrode electronic conductivity, most stable ion transport interface, and effective suppression of particle agglomeration and electrolyte side reactions, thus achieving theoretically optimal rate performance and cycle life. However, the trade-off is a significant dilution of volumetric and gravimetric energy densities. Lower carbon content (8:2): The active material accounts for up to 80%, significantly releasing the potential of mass and volumetric specific capacity. However, the carbon network may become discontinuous, the coating may be incomplete, leading to some active material being directly exposed to the electrolyte, and the electron transport path may become longer. This threatens rate performance and cycle stability. The significance of this range is that it defines the upper limit of the active material content that can be pursued while ensuring the minimum "effective conductivity and encapsulation" function. 8:2 (i.e., 20% carbon) is generally considered to be near the critical threshold for achieving effective carbon network coating, while 5:5 is the boundary for trading carbon content for ultimate performance stability.

[0082] II. Reaction Mechanism and Performance Realization: Predictable Performance Spectrum Guided by Proportion Range.

[0083] This range of proportions collectively determines the mechanochemical reaction products during the ball milling process, and ultimately maps to a predictable performance output spectrum.

[0084] Achieving "high capacity": The starting point of the entire design window is ensuring sufficient silicon content (this is ensured by the lower limit of the Si:P, Fe ratio). Both silicon-rich silicon-phosphorus compounds and nano-silicon encapsulated in thin layers provide the foundation for high capacity. By moving towards high Si:P ratios, low Fe content, and low carbon content (e.g., 8:2), the reversible capacity of materials can be systematically pushed to its peak.

[0085] Achieving "high magnification" relies on an efficient electron / ion transport network. This can be achieved by adjusting the proportions in a direction that enables the formation of a more continuous conductive phase: that is, increasing the Fe content to construct FeP. x The framework is improved, and / or the carbon content is increased to strengthen the carbon network. Although this will partially sacrifice capacity, it will result in a significant improvement in current carrying capacity.

[0086] Achieving "long cycle life" requires the most stable interface and the strongest stress management. Cycle life can be maximized by adjusting the combination of "higher P content (forming a robust phosphide interface), moderate to high Fe content (building a strong framework), and higher C content (providing rigid encapsulation)".

[0087] The advantages of the proportions we ultimately chose in terms of structural principles are: ① (Si+P) is much greater than Fe (molar ratio 8:1): This clearly indicates the design intent—iron (Fe) is not the primary active substance, but rather exists as a "structure guide" and "phosphide catalyst." The limited amount of Fe (molar ratio 1) will first react with some of the P to generate a small amount of FeP. x Nanocrystals. These FeP x Grains act as "seeds" or "connecting points" and are dispersed throughout the system.

[0088] ② Excess Si and P (4 each): Under the high-energy action of ball milling, excess Si and P will not only form nano-silicon particles, but also surround the already formed FeP x "Seeds," and the formation of amorphous or nanocrystalline silicon phosphide (SiP) directly on the Si surface. x The interface layer may ultimately form as Si@(SiP) x / FeP x Core-shell or embedded composite particles. Among them, SiP x / FeP x The mixed phase forms the first layer of buffer and conductive layer.

[0089] ③ A 7:3 mass ratio (active material: carbon): This ratio ensures a sufficiently high carbon content (~30 wt%). During ball milling, the carbon is not only coated onto each (Si@SiP) particle... x / FeP x On the surface of the composite particles, a dense second protective shell is formed. More importantly, it can be effectively sheared and spread, constructing a long-range, continuous three-dimensional conductive network among all the composite particles. If the carbon content is lower than this, the network is discontinuous; if it is higher, the active material will be excessively diluted, sacrificing volumetric energy density.

[0090] The advantages in terms of reaction mechanism are: the solid-phase reaction path in the ball milling process is highly dependent on the initial stoichiometric ratio, which directly leads to the optimal combination of reaction products.

[0091] ① The "catalytic" and "anchoring" effects of Fe (molar ratio Fe=1): Due to the low Fe content, it cannot bind with all P. Its primary role is to trigger and stabilize the formation of the phosphide phase. The generated FeP... x Exhibiting excellent metallic conductivity, FeP dispersed within materials provides a rapid pathway for electron transport. More importantly, FeP... x Can be combined with Si and SiP x Forming a robust interfacial bond to prevent silicon particles from detaching from the composite material during cycling is the chemical basis for achieving long-term cycling.

[0092] ② The construction of a "self-buffered" interface between Si and P (molar ratio Si:P = 1:1) allows for the large-scale formation of silicon phosphide (SiP) with equimolar amounts of Si and P. x The interface layer provides the stoichiometric basis. SiP x The mechanical properties of (especially amorphous) SiP fall between those of brittle Si and ductile metals, and the volume change of its lithiation products is much smaller than that of pure Si. In-situ generated SiP x The interface layer is the key mechanism for achieving high capacity and long cycle compatibility: it directly wraps around the Si core, which can more evenly transfer and buffer stress and suppress the cracking of the Si core; at the same time, it also has considerable lithium-ion conductivity, which ensures that Li⁺ can smoothly enter the internal Si core for reaction, thus without significantly sacrificing high capacity.

[0093] ③ The “global synergistic” role of the carbon network (mass ratio 7:3): The 30% carbon content is a global guarantee for achieving high rate capability and long cycle life. For rate capability: The continuous carbon network ensures that electrons can quickly reach each encapsulated composite particle from the current collector, greatly reducing the overall impedance of the electrode. For cycle life: The dense carbon coating layer is a physical barrier stabilizing the solid electrolyte interface (SEI). It greatly limits the direct and repeated contact between the electrolyte and the internal active materials (especially Si), thus confining the formation and growth of the SEI mainly to the outer surface of the carbon layer, forming a thin and stable SEI film, avoiding the continuous consumption of active lithium and electrolyte caused by the continuous breakage and regeneration of the SEI.

[0094] To facilitate understanding of the present invention, the technical solutions and advantages of the invention will be further described in detail below with reference to the accompanying drawings and embodiments. Example 1

[0095] The iron-based silicon-phosphorus composite anode material of Example 1 is prepared by the following steps: (1) Weigh elemental silicon powder, phosphorus powder and iron powder in an argon atmosphere glove box according to the molar ratio of silicon:phosphorus:iron of 2:2:1. Then weigh carbon material according to the mass ratio of carbon material to silicon-phosphorus-iron mixture of 7:3. The total mass of the mixture is 1.5 g. Then seal it into a stainless steel ball mill jar. (2) Weigh 20g of stainless steel beads with dimensions of 2, 3 and 5 mm respectively, and then package them into a stainless steel ball mill jar. (3) In a glove box with a high purity argon atmosphere, assemble a sealed ball mill jar with a stainless steel liner and use a planetary ball mill to mix and grind the elemental iron powder, elemental silicon powder, elemental phosphorus powder and carbon material in step (1); specifically, using gradient ball milling technology, firstly, perform preliminary physical mixing at 200 rpm and 300 rpm for 12 h each, and then perform high-energy ball milling at 450 rpm for 24 h. (4) Repeat step (3) ball milling at least twice to achieve uniform composite of silicon, phosphorus, iron and carbon elements at the nanoscale, thereby preparing iron-based silicon-phosphorus composite anode material with uniform particle size and uniform dispersion. Example 2

[0096] The iron-based silicon-phosphorus composite anode material of this embodiment 2 is prepared by the following steps: (1) Weigh elemental silicon powder, phosphorus powder and iron powder in an argon atmosphere glove box according to the molar ratio of silicon:phosphorus:iron of 4:4:1. Then weigh carbon material according to the mass ratio of carbon material to silicon-phosphorus-iron mixture of 7:3. The total mass of the mixture is 1.5 g. Then seal it into a stainless steel ball mill jar. (2) Weigh 20g of stainless steel beads with dimensions of 2, 3 and 5 mm respectively, and then package them into a stainless steel ball mill jar. (3) In a glove box with a high purity argon atmosphere, assemble a sealed ball mill jar with a stainless steel liner, and use a planetary ball mill to mix and grind the elemental iron powder, elemental silicon powder, elemental phosphorus powder and carbon material in step (1); specifically, using gradient ball milling technology, firstly, perform preliminary physical mixing at 200 rpm and 300 rpm for 12 h each, and then perform high-energy ball milling at 450 rpm for 24 h. (4) Repeat step (3) ball milling at least twice to achieve uniform composite of silicon, phosphorus, iron and carbon elements at the nanoscale, thereby preparing iron-based silicon-phosphorus composite anode material with uniform particle size and uniform dispersion. Example 3

[0097] The iron-based silicon-phosphorus composite anode material of this embodiment 3 is prepared by the following steps: (1) Weigh elemental silicon powder, phosphorus powder and iron powder in an argon atmosphere glove box according to the molar ratio of silicon:phosphorus:iron of 8:8:1, and weigh carbon material according to the mass ratio of carbon material to silicon-phosphorus-iron mixture of 7:3. The total mass of the mixture is 1.5 g, and then it is sealed into a stainless steel ball mill jar. (2) Weigh 20g of stainless steel beads with dimensions of 2, 3 and 5 mm respectively, and then package them into a stainless steel ball mill jar. (3) In a glove box with a high purity argon atmosphere, assemble a sealed ball mill jar with a stainless steel liner and use a planetary ball mill to mix and grind the elemental iron powder, elemental silicon powder, elemental phosphorus powder and carbon material in step (1); specifically, use gradient ball milling technology, first perform preliminary physical mixing at 200 rpm and 300 rpm for 12 h each, and then perform high-energy ball milling at 450 rpm for 24 h. (4) Repeat step (3) ball milling at least twice to achieve uniform composite of iron, silicon, phosphorus and carbon elements at the nanoscale, thereby preparing iron-based silicon-phosphorus composite anode material with uniform particle size and uniform dispersion. Example 4

[0098] The iron-based silicon-phosphorus composite anode material of Example 4 is prepared in a manner that is largely the same as that of Example 1. The difference is that the iron, silicon, and phosphorus used in Example 4 are nano-iron powder, nano-silicon powder, and nano-phosphorus powder, respectively. Example 5

[0099] The iron-based silicon-phosphorus composite anode material of Example 5 is prepared in a manner that is largely the same as that of Example 2. The difference is that the iron, silicon, and phosphorus used in Example 5 are nano-iron powder, nano-silicon powder, and nano-phosphorus powder, respectively. Example 6

[0100] The iron-based silicon-phosphorus composite anode material of Example 6 is prepared in a manner similar to that of Example 3, except that the iron, silicon, and phosphorus used in Example 6 are nano-iron powder, nano-silicon powder, and nano-phosphorus powder, respectively. Example 7

[0101] The iron-based silicon-phosphorus composite anode material of Example 7 is prepared in a manner similar to that of Example 1, except that: 1) the iron, silicon, and phosphorus used in Example 7 are nano-iron powder, nano-silicon powder, and nano-phosphorus powder, respectively; 2) the mass ratio of carbon material to silicon-phosphorus-iron mixture in Example 7 is 6:4. Example 8

[0102] The iron-based silicon-phosphorus composite anode material of Example 8 is prepared in a manner similar to that of Example 2, except that: 1) the iron, silicon, and phosphorus used in Example 8 are nano-iron powder, nano-silicon powder, and nano-phosphorus powder, respectively; 2) the mass ratio of carbon material to silicon-phosphorus-iron mixture in Example 8 is 6:4. Example 9

[0103] The iron-based silicon-phosphorus composite anode material of Example 9 is prepared in a manner similar to that of Example 3, except that: 1) the iron, silicon, and phosphorus used in Example 9 are nano-iron powder, nano-silicon powder, and nano-phosphorus powder, respectively; 2) the mass ratio of carbon material to silicon-phosphorus-iron mixture in Example 9 is 6:4. Example 10

[0104] The iron-based silicon-phosphorus composite anode material of Example 10 is prepared in a manner similar to that of Example 2. The difference is that when gradient ball milling is used in Example 10, the materials are first initially physically mixed at 200 rpm and 300 rpm for 12 hours each, and then high-energy ball milled at 400 rpm for 24 hours. Example 11

[0105] The iron-based silicon-phosphorus composite anode material of Example 11 is prepared in a manner similar to that of Example 2. The difference is that when gradient ball milling is used in Example 11, the material is first ball-milled at 200 rpm and 350 rpm for 12 h and 8 h respectively to achieve preliminary physical mixing, and then ball-milled at 450 rpm for 24 h. Example 12

[0106] The iron-based silicon-phosphorus composite anode material of Example 12 is prepared by the following steps: (1) Weigh elemental silicon powder, phosphorus powder and iron powder in an argon atmosphere glove box according to the molar ratio of silicon:phosphorus:iron of 2:2:1; (2) Weigh 20g of each of stainless steel beads with dimensions of 2, 3 and 5 mm respectively; (3) Transfer the raw materials weighed in step (1) and the grinding balls weighed in step (2) to a stainless steel ball mill jar and seal and assemble them in a glove box under an argon atmosphere. (4) Using gradient ball milling technology, the mixture was first physically mixed at 200 rpm and 300 rpm for 12 hours each, and then high-energy ball milled at 450 rpm for 24 hours. (5) Repeat step (4) ball milling at least twice to achieve uniform composite of silicon, phosphorus and iron at the nanoscale, thereby obtaining iron-silicon-phosphorus anode material.

[0107] (6) Weigh the carbon material according to the mass ratio of silicon-phosphorus-iron mixture to carbon material of 7:3, add the carbon material and the prepared iron-silicon-phosphorus anode material together into a stainless steel ball mill jar, and seal and assemble them in an argon atmosphere glove box. (7) Using gradient ball milling technology, firstly, ball milling is carried out at 200 rpm and 300 rpm for 12 hours respectively to achieve preliminary physical mixing, and then high-energy ball milling is carried out at 450 rpm for 24 hours. (8) Repeat step (7) ball milling at least twice to achieve uniform composite of iron, silicon, phosphorus and carbon elements at the nanoscale, thereby obtaining iron-based silicon-phosphorus composite anode material with uniform particle size and uniform dispersion. Example 13

[0108] The iron-based silicon-phosphorus composite anode material of Example 13 is prepared in a manner that is largely the same as that of Example 12, except that the silicon:phosphorus:iron molar ratio in Example 13 is 4:4:1. Example 14

[0109] The iron-based silicon-phosphorus composite anode material of Example 14 is prepared in a manner that is largely the same as that of Example 13. The difference is that the iron, silicon, and phosphorus used in Example 14 are nano-iron powder, nano-silicon powder, and nano-phosphorus powder, respectively. Example 15

[0110] The iron-based silicon-phosphorus composite anode material of Example 15 is prepared in a manner largely the same as that of Example 4, with the following differences: 1) The silicon:phosphorus:iron molar ratio of Example 15 was 1:1:2; 2) The mass ratio of carbon material to silicon-phosphorus-iron mixture in Example 15 is 5:5; 3) 25g each of the 2mm, 3mm and 5mm stainless steel beads from Example 15; 4) Step (4) of Example 15 is to first perform preliminary physical mixing at 100 rpm and 200 rpm for 12 h each, and then perform high-energy ball milling at 350 rpm for 24 h.

[0111] Example 16 The iron-based silicon-phosphorus composite anode material of Example 16 is prepared in a method that is largely the same as that of Example 4, except that: 1) The silicon:phosphorus:iron molar ratio of Example 16 was 2:3:3; 2) The mass ratio of carbon material to iron-silicon-phosphorus mixture in Example 16 is 8:2; 3) 15g each of the 2mm, 3mm and 5mm stainless steel beads from Example 16; 4) Step (4) of Example 16 is to first perform preliminary physical mixing at 150 rpm and 250 rpm for 8 hours each, and then perform high-energy ball milling at 500 rpm for 36 hours.

[0112] Example 17 The iron-based silicon-phosphorus composite anode material of Example 17 is prepared in a manner largely the same as that of Example 4, except that: 1) The silicon:phosphorus:iron molar ratio of Example 17 was 5:10:1; 2) The mass ratio of carbon material to silicon-phosphorus-iron mixture in Example 17 is 8:2; 3) 10g each of the 2mm, 3mm and 5mm stainless steel beads from Example 17; 4) Step (4) of Example 17 is to first perform preliminary physical mixing at 150 rpm and 300 rpm for 18 h each, and then perform high-energy ball milling at 600 rpm for 12 h. Comparative Example 1

[0113] The silicon-phosphorus composite material of Comparative Example 1 is prepared by the following steps: (1) Weigh silicon powder and phosphorus powder in an argon atmosphere glove box according to a silicon:phosphorus molar ratio of 1:1, and then weigh carbon material according to a carbon material to silicon-phosphorus mixture mass ratio of 7:3. The total mass of the mixture is 1.5 g, and then it is sealed into a stainless steel ball mill jar. (2) Weigh 20g of stainless steel beads with dimensions of 2, 3 and 5 mm respectively, and then package them into a stainless steel ball mill jar. (3) In a glove box with a high purity argon atmosphere, a sealed ball mill jar with a stainless steel liner is assembled, and a planetary ball mill is used to mix and grind the elemental silicon powder, elemental phosphorus powder and carbon material in step (1); specifically, gradient ball milling technology is adopted, firstly, ball milling is carried out at 200 rpm and 350 rpm for 24 hours respectively to achieve preliminary physical mixing, and then high-energy ball milling is carried out at 450 rpm for 48 hours; (4) Repeat step (3) ball milling at least twice to achieve uniform composite of silicon, phosphorus and carbon elements at the nanoscale, thereby preparing silicon / phosphorus composite anode material. Electrochemical performance testing

[0114] The materials prepared in Examples 1-14 and Comparative Example 1 were used to fabricate negative electrodes and assembled into batteries. The cycle performance of the batteries was tested. The specific method is as follows: The iron-based silicon-phosphorus composite negative electrode material and silicon-phosphorus negative electrode material prepared in each example and comparative example were cut into negative electrode sheets. A lithium metal sheet was used as the counter electrode, and a PP / PE / PP type composite membrane was used as the separator. An ethylene carbonate (EC) / dimethyl carbonate (DMC) / ethyl methyl carbonate (EMC) solution (volume ratio 1:1:1) containing 1 mol / L LiPF6 electrolyte and 10 vol.% fluoroethylene carbonate (FEC) and 2 vol.% vinylene carbonate (VC) was added as the electrolyte. The negative electrode sheets were assembled into CR2032 coin cells in an argon-filled glove box. The assembled batteries were then subjected to 0.5 Ag... -1 The battery was cycled 300 times at a current density, and its initial charge specific capacity and the charge specific capacity after 50 and 300 cycles were tested, as shown in Table 1 below. The assembled battery was then subjected to a 1 A g test. -1The battery was cycled 600 times at a current density, and its initial charge specific capacity and the charge specific capacity after 100 and 600 cycles were tested, as shown in Table 2. The assembled battery was cycled 100 times at a current density of 2 and 1000 times at a current density of 100 and 1000 cycles, and its initial charge specific capacity and the charge specific capacity after 100 and 1000 cycles were tested, as shown in Table 3. The assembled battery was cycled at 5 A g... -1 The battery was cycled 2000 times at a current density, and its initial charge specific capacity and the charge specific capacity after 100 and 2000 cycles were tested, as shown in Table 4 below. The assembled battery was tested at 10 A g. -1 The batteries were cycled 8000 times at a current density as shown in Table 5 below. The assembled batteries from Examples 4-6 and Comparative Example 1 were then subjected to a current density of 0.2 A g. -1 0.5 A g -1 1 A g -1 2 A g -1 5 A g -1 10 A g -1 20 A g -1 The initial charge specific capacity was tested by cycling ten times at each current density, as shown in Table 6 below.

[0115] The materials prepared in Example 5 were used to fabricate negative electrodes, and NCM811 was used as the positive electrode material to assemble a full cell. The cycle performance of the battery was tested. The specific method is as follows: The iron-based silicon-phosphorus negative electrode material prepared in Example 5 was cut into negative electrode sheets, and the NCM811 positive electrode material was cut into positive electrode sheets as counter electrodes. The negative electrode sheets were subjected to contact pre-lithiation. A PP / PE / PP type composite membrane was used as the separator. An ethylene carbonate (EC) / dimethyl carbonate (DMC) / ethyl methyl carbonate (EMC) solution (volume ratio 1:1:1) containing 1 mol / L LiPF6 electrolyte and 10 vol.% fluoroethylene carbonate (FEC) and 2 vol.% vinylene carbonate (VC) was added as the electrolyte. The negative electrode sheets were assembled into CR2032 coin cells in an argon-filled glove box. The assembled cells were tested at 0.1 and 0.2 A g. -1 The initial charge specific capacity and the charge specific capacity after 50 and 300 cycles were tested under the current density, as shown in Table 1 below.

[0116] Table 1. Composite anode materials of each embodiment and comparative example at 0.5 A g. -1 Electrochemical performance under project <![CDATA[Initial charge specific capacity (mAh g -1 )]]> <![CDATA[Specific capacity after 50 cycles (mAh g -1 )]]> <![CDATA[Specific capacity after 300 cycles (mAh g -1 )]]> First lap Coulomb efficiency specific capacity retention after 50 cycles specific capacity retention after 300 cycles Example 1 1650.59 1406.70 1331.92 81.32% 85.23% 80.69% Example 2 1710.53 1214.81 1037.41 82.54% 71.02% 60.65% Example 3 1670.01 1432.16 1317.02 83.54% 85.76% 78.86% Example 4 1436.98 1156.34 1187.52 80.26% 80.47% 82.64% Example 5 1776.32 1629.51 1589.76 86.49% 91.74% 89.50% Example 6 1650.59 1406.70 1343.89 82.29% 85.23% 81.41% Example 7 1359.36 1210.85 1089.99 83.25% 89.08% 80.18% Example 8 1496.86 1214.46 1191.28 80.73% 81.13% 79.58% Example 9 1415.35 1149.32 1054.52 80.14% 81.20% 74.51% Example 10 1746.38 1420.33 1229.80 82.68% 81.33% 70.42% Example 11 1673.74 1373.18 1309.40 83.54% 82.78% 79.66% Example 12 1688.56 1294.45 1189.59 81.68% 76.66% 70.45% Example 13 1748.89 1443.88 1309.91 82.25% 82.56% 74.90% Example 14 1689.21 1323.32 1171.46 80.62% 78.34% 69.35% Comparative Example 1 1719.37 1449.21 1387.42 80.16% 84.28% 80.69 % Table 1 shows the composite anode materials of each embodiment and comparative example at 0.5 Ag. -1Cyclic electrochemical performance at current density. Among the 14 examples and 1 comparative example listed, Example 5 showed significant advantages in all performance indicators: it had the highest initial charge specific capacity, reaching 1776.32 mAhg. -1 After 50 cycles, the capacity retention rate was 91.74% (1629.51 mAh g). -1 It still maintains 1589.76 mAhg after 300 cycles. -1 (Capacity retention rate 89.50%), while the first-cycle coulombic efficiency is 86.49%, demonstrating excellent structural stability and capacity retention. Examples 3 and 6 respectively have high initial capacities (1670.01 mAh g⁻¹). -1 and 1650.59 mAhg -1 After 300 cycles, the retention rates were 78.86% and 81.41%, respectively, demonstrating good cycle durability. Although Examples 1, 4, 7, 8, and 11 had slightly lower initial capacities, their retention rates after 300 cycles were all between 79% and 83%, indicating good cycle stability. Examples 2 and 10 are noteworthy, as they had relatively high initial capacities (1710.53 mAh g⁻¹, respectively). -1 and 1746.38 mAhg -1 However, after 300 cycles, the retention rates decreased to 60.65% and 70.42%, respectively, indicating that its capacity decay was relatively rapid during long-term cycling. Comparative Example 1 had an initial capacity of 1719.37 mAh g⁻¹. -1 Similar to some embodiments, but with retention rates of 84.28% and 80.69% after 50 and 300 cycles respectively, slightly lower than that of Embodiment 5, indicating that the present invention has advantages in terms of structural design or material composition.

[0117] The product of this invention exhibits high reversible specific capacity. Precise proportions maximize the retention of active silicon content while constructing a robust buffer network, and the interface phase itself also contributes to capacity. Precise stoichiometry design achieves an optimal balance between the proportion of active material and structural stability. It exhibits higher first-efficiency and coulombic efficiency. Stable SiP. x / FeP x The interface and dense carbon layer effectively inhibit electrolyte decomposition, forming a thinner and more stable SEI film. This results in more stable material surface and interface chemistry.

[0118] In summary, at 0.5 Ag -1 Under the test conditions, Example 5 not only leads in initial capacity but also exhibits excellent capacity retention and structural stability in both short-cycle and long-cycle conditions, making it the most outstanding component in this material system. The rate performance diagrams for Examples 4, 5, 6, and Comparative Example 1 are shown below. Figure 14This indicates that the method of the present invention can alleviate the volume expansion of silicon during cycling and improve the cycle stability of the battery. It also shows that the method of the present invention introduces red phosphorus into silicon-carbon composite materials, which can make the prepared materials still have good cycle performance and high capacity retention even with high silicon content. The introduced iron provides a channel for lithium-ion transport, accelerates electron transfer and lithium-ion transport rate, enhances the conductivity of the material, and at the same time acts as a buffer layer to alleviate the stress released by the volume expansion of silicon materials.

[0119] Table 2 shows the composite anode materials of Examples 4-6 and Comparative Example 1 at 1 A g. -1 Electrochemical performance under project <![CDATA[Initial charge specific capacity (mAh g -1 )]]> <![CDATA[Specific capacity after 100 cycles (mAh g -1 )]]> <![CDATA[Specific capacity after 600 cycles (mAh g -1 )]]> First lap Coulomb efficiency Capacity retention after 100 cycles specific capacity retention after 600 cycles Example 4 1210.99 926.77 1063.58 79.91 76.52% 87.8% Example 5 1506.30 1182.50 1152.78 81.52 78.50% 76.53% Example 6 1469.13 1092.04 819.44 79.92 74.33% 55.77% Comparative Example 1 1546.29 106.73 47.81 79.90 6.90% 3.09% As can be seen from Table 2, Examples 4, 5, 6 and Comparative Example 1 were in 1A g -1 See the cycling performance diagram at current density. Figure 8 Example 5 in 1 A g -1 After 100 cycles at the current density, it has a capacity of 1182.50 mAh g. -1 It boasts reversible capacity with a capacity retention rate of up to 78.5%, still retaining 1152.78 mAh g after 600 cycles. -1 The reversible capacity above has a capacity retention rate of 76.53%; Comparative Example 1 at 1A g -1 After 100 cycles at the current density, it only has 106.73 mAh g⁻¹. -1 The capacity retention rate was only 6.90%, and after 600 cycles, it was 47.81 mAh g. -1 The capacity retention rate was 3.09%.

[0120] Table 3. Composite anode materials of Examples 4-6 and Comparative Example 1 at 2 A g -1 Electrochemical performance under project <![CDATA[Initial charge specific capacity (mAh g -1 )]]> <![CDATA[Specific capacity after 100 cycles (mAh g -1 )]]> <![CDATA[Specific capacity after 1000 cycles (mAh g -1 )]]> First lap Coulomb efficiency Capacity retention after 100 cycles Capacity retention after 1000 cycles Example 4 969.50 886.24 935.62 80.39% 91.41% 96.51% Example 5 1095.50 1049.07 1059.62 87.96% 95.76% 96.73% Example 6 1148.47 1117.90 683.75 82.19% 97.34% 59.53% Comparative Example 1 324.63 106.73 47.81 83.89% 32.87% 14.47% As shown in Table 3, among the four sample groups, Example 5 once again exhibited excellent electrochemical performance, with an initial charge specific capacity of 1095.50 mAh g⁻¹. -1 After 100 cycles, the capacity remains at 1049.07 mAh g. -1 (Retention rate 95.76%), and after 1000 cycles, the retention rate reached as high as 96.73% (1059.62 mAh g). -1 The initial coulombic efficiency was 87.96%, demonstrating high capacity retention and structural stability. Example 6 exhibited the highest initial charge specific capacity (1148.47 mAh g). -1 The retention rate after 100 cycles was 97.34% (1117.90 mAh g).-1 However, after 1000 cycles, the capacity rapidly decreased to 683.75 mAh g. -1 The retention rate dropped to 59.53%, indicating that its stability during long-term cycling still needs improvement. Example 4 had an initial capacity of 969.50 mAh g. -1 Its cycling stability is outstanding, retaining 91.41% after 100 cycles and even slightly recovering to 96.51% after 1000 cycles, demonstrating good structural reversibility and cycle durability. Comparative Example 1 performed the worst, with an initial capacity of only 324.63 mAh g⁻¹. -1 Furthermore, its capacity decayed significantly during cycling; after 100 cycles, the retention rate was only 32.87%, and after 1000 cycles, the retention rate dropped sharply to 14.47%, indicating that its electrochemical stability and capacity retention at high rates were significantly insufficient. In summary, at 2Ag... -1 At current density, Example 5 not only has high initial capacity, but also a long-cycle retention rate of nearly 97%, making it a preferred material system that combines high capacity and excellent cycle stability.

[0121] Table 4. Composite anode materials of Examples 4-6 and Comparative Example 1 at 5 A g -1 Electrochemical performance under project <![CDATA[Initial charge specific capacity (mAh g -1 )]]> <![CDATA[Specific capacity after 100 cycles (mAh g -1 )]]> <![CDATA[Specific capacity after 2000 cycles (mAh g -1 )]]> First lap Coulomb efficiency Capacity retention after 100 cycles specific capacity retention after 2000 cycles Example 4 926.85 730.17 627.78 85.49% 78.78% 67.73% Example 5 1105.51 939.04 870.81 87.96% 84.94% 78.77% Example 6 928.21 739.61 629.15 81.71% 79.68% 67.78% Comparative Example 1 47.24 30.57 29.18 84.67% 64.71% 61.77% As shown in Table 4, Example 5 exhibits the best overall performance, with an initial charge specific capacity of 1105.51 mAh g. -1 After 100 cycles, the capacity remained at 939.04 mAh g. -1 (Retention rate 84.94%), still reaching 870.81 mAh g after 2000 cycles. -1 (Retention rate 78.77%), with a first-cycle coulombic efficiency of 87.96%, demonstrating good structural stability and high capacity retention. The initial capacities of Examples 4 and 6 are comparable, at 926.85 mAh g⁻¹. -1 and 928.21mAhg -1 After 100 cycles, the capacity retention rates were 78.78% and 79.68%, respectively, and after 2000 cycles, they remained at 67.73% and 67.78%, respectively. The cycle stability of both examples was similar, but their capacity and retention rates were significantly lower than those of Example 5. Comparative Example 1 showed a significant performance decrease, with an initial charge specific capacity of only 47.24 mAhg. -1 After 100 and 2000 cycles, the retention rates were 64.71% and 61.77%, respectively, indicating that its electrochemical performance at high rates was significantly lower than other embodiments. Structural or compositional defects are likely the main reasons for its low capacity and rapid decay. Overall, at 5Ag... -1Under high-rate conditions, Example 5 not only demonstrates a significant advantage in initial capacity but also exhibits excellent performance in long-cycle stability and capacity retention, making it the most promising component in this material system. Table 5. Composite anode materials of Examples 4-6 and Comparative Example 1 at 10 A g -1 Electrochemical performance under project <![CDATA[Initial charge specific capacity (mAh g -1 )]]> <![CDATA[Specific capacity after 1000 cycles (mAh g -1 )]]> <![CDATA[Specific capacity after 8000 cycles (mAh g -1 )]]> First lap Coulomb efficiency Capacity retention after 1000 cycles specific capacity retention after 8000 cycles Example 4 507.68 347.86 319.70 79.13% 68.52% 62.97% Example 5 719.90 694.86 605.94 82.38% 96.52% 84.17% Example 6 106.09 50.01 85.64 79.01% 47.14% 80.72% Comparative Example 1 106.09 38.31 85.46 80.45% 36.11% 80.55% As shown in Table 5, the initial charge specific capacity and long-cycle performance data indicate that Example 5 exhibits the highest specific capacity (719.90 mAh g⁻¹) during the first charge-discharge cycle. -1 It can maintain 694.86 mAh g after 1000 cycles. -1 The specific capacity (retention rate 96.52%) was maintained at 84.17% (605.94 mAh g⁻¹) after 8000 cycles. -1 This demonstrates excellent cycling stability and capacity retention. Example 4 showed an initial capacity of 507.68 mAh g⁻¹. -1 The cycle retention rate was relatively low (68.52% after 1000 cycles and 62.97% after 8000 cycles), but it still maintained a considerable capacity (319.70 mAh g). -1 The initial specific capacity of both Example 6 and Comparative Example 1 was low (approximately 106.09 mAh g⁻¹). -1 After 1000 cycles, the capacity retention rates of the two samples decreased significantly (to 47.14% and 36.11%, respectively), but after 8000 cycles, both retention rates rebounded to over 80%, which may be due to the material structure stabilizing in the later stages of cycling. In terms of the coulombic efficiency in the first cycle, all samples were between 79% and 82%, with little difference. Overall, Example 5 not only has a high initial capacity but also exhibits slow capacity decay over long cycles, making it the sample with the best overall performance.

[0122] The product of this invention exhibits extremely long cycle life and high capacity retention at high current densities. This is due to the chemically bonded FeP... x / SiP x The interface and integrated carbon network synergistically and persistently suppress volume expansion, maintaining structural integrity. Strong chemically bonded interfaces and an integrated buffer / conductive network are key features.

[0123] Table 6 Rate performance of the composite anode materials of Examples 4-6 and Comparative Example 1 at different current densities. project <![CDATA[0.2 A g -1 Initial charge specific capacity (mAh g) -1 )]]> <![CDATA[0.5 A g -1 Initial charge specific capacity (mAh g) -1 )]]> <![CDATA[1 A g -1 Initial charge specific capacity (mAh g) -1 )]]> <![CDATA[2 A g -1 Initial charge specific capacity (mAh g) -1 )]]> <![CDATA[5 A g -1 Initial charge specific capacity (mAh g) -1 )]]> <![CDATA[10 A g -1 Initial charge specific capacity (mAh g) -1 )]]> <![CDATA[20 A g -1 Initial charge specific capacity (mAh g) -1 )]]> Example 4 1484.14 1321.97 1116.67 932.84 788.55 494.80 208.07 Example 5 1819.52 1626.04 1417.03 1284.11 1016.26 784.31 489.95 Example 6 1981.68 1626.04 1417.63 1136.47 788.55 129.87 22.94 Comparative Example 1 1745.54 1109.14 922.32 750.93 504.58 113.94 13.60 As shown in Table 6, based on the rate performance data of Examples 4, 5, 6 and Comparative Example 1 at different current densities (table omitted, content is initial charge specific capacity), at 0.2 A g -1At the given current density, the initial charge specific capacity of each sample was as follows: Example 4 (1484.14 mAh g⁻¹) -1 Example 5 (1819.52 mAh g) -1 Example 6 (1981.68 mAh g) -1 Comparative Example 1 (1745.54 mAh g) -1 When the multiplier is increased to 0.5 A g -1 At that time, the capacities were 1321.97, 1626.04, 1626.04, and 1109.14 mAh g, respectively. -1 ;1 A g -1 At that time, the values ​​were 1116.67, 1417.03, 1417.63, and 922.32 mAh g. -1 ;2 A g -1 At that time, the values ​​were 932.84, 1284.11, 1136.47, and 750.93 mAh g. -1 5 A g -1 At that time, the values ​​were 788.55, 1016.26, 788.55, and 504.58 mAh g. -1 .

[0124] When the current density is further increased to 10 A g -1 At that time, Example 5 (784.31 mAh g) -1 The capacity remains high, while Example 6 (129.87 mAh g) still maintains a high capacity. -1 ) and Comparative Example 1 (113.94 mAh g) -1 The capacity of ) decreased sharply. At 20 Ag -1 At the limiting rate of increase, Example 5 (489.95 mAh g) -1 ) exhibited excellent limiting rate performance, while Example 6 (22.94 mAh g) -1 ) and Comparative Example 1 (13.60 mAh g) -1 The capacity of Example 5 was almost completely lost, indicating that Example 5 has more stable electrochemical performance under rapid charge and discharge conditions.

[0125] The product of this invention exhibits excellent high-rate performance. This is due to the in-situ generation of highly conductive FeP and a gradient interface (Si-SiP). x -FeP-C) provides a seamless high-speed electron / ion transport channel.

[0126] Table 7. Example 5: Composite anode material assembled into a full cell at 0.1 and 0.2 A g. -1 Electrochemical performance under project <![CDATA[Initial discharge specific capacity (mAh g -1 )]]> <![CDATA[Specific capacity after 100 cycles (mAh g -1 )]]> <![CDATA[Specific capacity after 300 cycles (mAh g -1 )]]> First lap Coulomb efficiency Capacity retention after 100 cycles specific capacity retention after 300 cycles <![CDATA[Example 5 (0.1 A g -1 )]]> 175.29 128.06 105.98 62.84% 73.05% 60.45% <![CDATA[Example 5 (0.2 A g -1 )]]> 167.87 125.14 102.56 65.26% 74.54% 61.09% Table 7 shows the iron-based silicon-phosphorus composite material prepared in this invention at 0.1 A g. -1 and 0.2 Ag -1 Electrochemical performance of the assembled full cell at current density. At 0.1 A g... -1 At the given current density, the initial discharge specific capacity of the full cell in Example 5 was 175.29 mAh g⁻¹. -1 The initial coulomb efficiency was 62.84%; after 100 cycles, the capacity was 128.06 mAh g. -1 The capacity retention rate was 73.05%; after 300 cycles, the capacity was 105.98 mAh g. -1 The capacity retention rate was 60.45%. (At 0.2A g) -1 At the given current density, the initial discharge specific capacity of the full cell in Example 5 was 167.87 mAh g⁻¹. -1 The initial coulomb efficiency improved to 65.26%; after 100 cycles, the capacity was 125.14 mAh g. -1 The capacity retention rate was 74.54%; after 300 cycles, the capacity remained at 102.56 mAh g. -1 The capacity retention rate was 61.09%. The results indicate that this material has good practical application potential in full-cell systems, especially in maintaining a relatively stable capacity during medium-term cycling.

[0127] Table 8 Rate performance of the iron-based silicon-phosphorus composite anode assembled full cell prepared in this invention at different current densities. project <![CDATA[0.04 A g -1 Initial discharge specific capacity (mAh g) -1 )]]> <![CDATA[0.1 A g -1 Initial discharge specific capacity (mAh g) -1 )]]> <![CDATA[0.2 A g -1 Initial discharge specific capacity (mAh g) -1 )]]> <![CDATA[0.4 A g -1 Initial discharge specific capacity (mAh g) -1 )]]> <![CDATA[1 A g -1 Initial discharge specific capacity (mAh g) -1 )]]> Example 5 180.63 152.36 140.60 130.20 115.69 The all-electric cell assembled from the composite material prepared in Example 5 has a compatibility of 0.04-1 A g. -1 See the rate performance graph at current density. Figure 27 The all-electric battery assembled from the composite material prepared in Example 5 has a capacitance of 0.04-1 A g. -1 The charge-discharge curves at current density are shown below. Figure 28 In Example 5 of the present invention, a full cell assembled with a commercially available cathode was used at 0.04 A g. -1 Up to 1.0 A g -1 It exhibits excellent rate performance and capacity retention over a wide current density range. At 0.04 A g... -1 At low rates, the initial discharge specific capacity of the full battery is as high as 180.63 mAh g⁻¹. -1 When the current density is increased to 0.1 A g -1 At that time, the capacity remained at 152.36 mAh g. -1This represents 53.4% ​​of the capacity at low rates; when the current density is increased to 0.2 A g... -1 At that time, the capacity remained at 140.60 mAh g. -1 When the current density is increased to 0.4 A g -1 At that time, the capacity remained at 130.20 mAh g. -1 When the current density increases to 1 A g -1 At that time, the capacity remained at 115.69 mAh g. -1 As the current increases, the voltage polarization between the charge and discharge curves gradually increases, but the growth trend is gradual, reaching 1.0 A g. -1 No severe distortion or breakage of the voltage plateau was observed, reflecting that the electrode has low charge transfer impedance and relatively fast ion diffusion capability. After a series of high-rate tests, when the current density returned to 0.04 A g... -1 At that time, its charge-discharge curve was similar to that of 0.1 Ag. -1 The following ratio curves highly overlap.

[0128] Based on electrochemical performance testing, further generation Figure 1-28 The following is a description and analysis of each of the attached figures.

[0129] Figure 1 The XRD patterns of the composite materials prepared by Examples 4, 5, 6 and Comparative Example 1 are shown, illustrating the X-ray diffraction patterns of Examples 4, 5, 6 and Comparative Example 1 of the present invention. Figure 1 As shown, all samples exhibited the characteristic (111) diffraction peak of crystalline silicon (Si) at approximately 28.5°, confirming the presence of silicon active materials. Simultaneously, characteristic diffraction peaks of the iron (Fe) phase were visible in the spectra. Compared to Comparative Example 1, the diffraction patterns of Examples 4-6 of this invention showed significant differences in the iron phase diffraction region (44°-85°). This result indicates that the preparation method of the iron-based silicon-phosphorus composite anode material provided by this invention optimizes the interfacial bonding and distribution between the silicon and iron phases. This microstructure regulation helps to form a more robust conductive network and buffer volume expansion, which corroborates the excellent electrochemical performance (high initial efficiency, long cycle life) exhibited in Examples 5 and 6.

[0130] Figure 2 The XPS full spectrum of the composite materials prepared by Examples 4, 5, 6 and Comparative Example 1 is shown. The spectrum clearly shows that all the sample samples contain the three core elements Si, Fe and C. The XPS results show that the addition of an appropriate amount of Fe can enhance the Fe-P bond and thus promote the charge transfer process.

[0131] Figure 3The figure shows the Fe 2p XPS spectra of the composite materials prepared by Examples 4, 5, 6 and Comparative Example 1. The figure shows that the Fe-P bonds and the percentage of iron content in different valence states are different in Examples 4, 5 and 6. Among them, Example 5 has the highest Fe-P bond content. This XPS shows that the addition of an appropriate amount of Fe can enhance the Fe-P bond and thus promote the charge transfer process.

[0132] Figure 4 The XPS spectra of the composite materials prepared in Examples 4, 5, 6, and Comparative Example 1 are shown. These XPS spectra clearly demonstrate that the technical solutions of this invention (Examples 4, 5, and 6) successfully formed a phosphate-rich interface layer or coating layer in situ on the material surface.

[0133] Figure 5 The images show the Si 2p XPS spectra of the composite materials prepared in Examples 4, 5, 6, and Comparative Example 1. The fine XPS spectra indicate that the optimized process of this invention (Examples 4, 5, and 6) effectively controlled the oxidation state of the silicon material surface, resulting in high-binding-energy Si... 4+ The peak was significantly weakened, indicating a reduction in electrochemically inert components and intermediate valence state silicon oxide (Si). + Si 2+ Si 3+ The presence and changes of ) may correspond to a thinner, more stable, and ionicly conductive primary oxide layer or interface phase.

[0134] Figure 6 Raman spectra of the composite materials prepared in Examples 4, 5, 6, and Comparative Example 1. Figure 6 As can be seen, the present invention introduces more carbon atoms with sp³ hybridization, structural defects, or smaller graphite microcrystals into the material. The introduction of Fe reduces the crystallinity of the material and induces structural disorder. This moderately increased structural disorder and defect density is generally beneficial in lithium battery anodes.

[0135] Figure 7 The composite materials prepared in Examples 4, 5, 6 and Comparative Example 1 were subjected to a concentration of 0.5 A g. -1 Cyclic performance graph at current density. (From...) Figure 7 As can be seen from Table 1, in Example 4, at 0.5 A g -1 After 50 cycles at the current density, it has a capacity of 1156.34 mAh g. -1 It exhibits reversible capacity with a capacity retention rate of 80.47%, and retains 1187.52 mAh g after 300 cycles. -1The above reversible capacity has a capacity retention rate of 82.64% and a first-cycle coulombic efficiency of 80.26%; Example 5 uses 0.5 Ag. -1 After 50 cycles at the current density, it has a capacity of 1629.51 mAh g. -1 It boasts reversible capacity with a capacity retention rate of up to 91.74%, still retaining 1589.76 mAh g after 300 cycles. -1 The above reversible capacity has a capacity retention rate of 89.50% and a first-cycle coulombic efficiency of 86.49%; Example 6 uses 0.5 Ag. -1 After 50 cycles at the current density, it has a capacity of 1406.70 mAh g. -1 It exhibits reversible capacity with a capacity retention rate of 85.23%, retaining 1343.89 mAh g after 300 cycles. -1 The reversible capacity was 81.41%, with a first-cycle coulombic efficiency of 82.29%; Comparative Example 1 was at 0.5 Ag. -1 After 50 cycles at the current density, it has a capacity of 1449.21 mAh g. -1 The capacity retention rate was 84.28%, and after 300 cycles, it was 1387.42 mAh g. -1 The capacity retention rate was 80.69%, and the first-round coulomb efficiency was 80.16%.

[0136] Figure 8 The composite materials prepared in Examples 4, 5, 6 and Comparative Example 1 were subjected to a reaction at 1 A g. -1 Cyclic performance graph at current density. (From...) Figure 8 As can be seen from Table 2, in Example 4, 1 A g -1 After 100 cycles at the current density, it has a capacity of 926.77 mAh g. -1 It exhibits reversible capacity with a capacity retention rate of 76.52%, and retains 1063.58 mAh g after 600 cycles. -1 The above reversible capacity has a capacity retention rate of 87.8%; Example 5 at 1 A g -1 After 100 cycles at the current density, it has a capacity of 1182.50 mAh g. -1 It boasts reversible capacity with a capacity retention rate of up to 78.5%, still retaining 1152.78 mAh g after 600 cycles. -1 The above reversible capacity has a capacity retention rate of 76.53%; Example 6 at 1 A g -1 After 100 cycles at the current density, it has a capacity of 1092.04 mAh g. -1It exhibits reversible capacity retention of 74.33%, and still retains 819.44 mAh g after 600 cycles. -1 The reversible capacity was maintained at 55.77%; Comparative Example 1 at 1A g -1 After 100 cycles at the current density, it only has 106.73 mAh g⁻¹. -1 The capacity retention rate was only 6.90%, and after 600 cycles, it was 47.81 mAh g. -1 The capacity retention rate was 3.09%.

[0137] Figure 9 The composite materials prepared in Examples 4, 5, 6 and Comparative Example 1 were subjected to a reaction at 2 A g. -1 Cyclic performance graph at current density. (From...) Figure 9 As can be seen from Table 3, in Example 4, 2 A g -1 After 100 cycles at the current density, it has a capacity of 886.24 mAh g. -1 The reversible capacity retains 91.41% of the capacity, and still has 935.62 mAh g after 1000 cycles. -1 The reversible capacity was maintained at 96.51%; Example 5 showed a capacity retention of 96.51% at 2 A g. -1 After 100 cycles at the current density, it has a capacity of 1049.07 mAh g. -1 It exhibits reversible capacity with a capacity retention rate of up to 95.76%, and still retains 1059.62 mAh g after 1000 cycles. -1 The above reversible capacity has a capacity retention rate of 96.73%; Example 6 at 2 A g -1 After 100 cycles at the current density, it has a capacity of 117.90 mAh g. -1 It exhibits reversible capacity with a capacity retention rate of 97.34%, retaining 683.75 mAh g after 1000 cycles. -1 The reversible capacity was maintained at 59.93%; Comparative Example 1 at 2 A g -1 After 100 cycles at the current density, it only has 106.73 mAh g⁻¹. -1 The capacity retention rate was only 32.87%, and after 1000 cycles it was 47.81 mAh g. -1 The capacity retention rate was only 14.47%.

[0138] Figure 10 The composite materials prepared in Examples 4, 5, 6 and Comparative Example 1 were subjected to a reaction at 5 A g. -1 Cyclic performance graph at current density. (From...) Figure 10 As can be seen from Table 4, in Example 4, at 5 A g -1 After 100 cycles at the current density, it has a capacity of 730.17 mAh g. -1 It exhibits reversible capacity with a capacity retention rate of 78.78%, retaining 627.78 mAh g after 2000 cycles. -1 The reversible capacity was maintained at 67.73%; Example 5 showed a capacity retention of 67.73% at 5 A g. -1 After 100 cycles at the current density, it has a capacity of 939.04 mAh g. -1 It exhibits reversible capacity with a capacity retention rate of up to 84.94%, and still retains 870.81 mAh g after 2000 cycles. -1 The above reversible capacity has a capacity retention rate of 78.77%; Example 6 at 5 A g -1 After 100 cycles at the current density, it has a capacity of 739.61 mAh g. -1 The reversible capacity retains 64.71% of its capacity, and after 2000 cycles, it still has 629.15 mAh g⁻¹. -1 The reversible capacity was maintained at 61.77%; Comparative Example 1 at 5 A g -1 After 100 cycles at the current density, it only has 30.57 mAh g⁻¹. -1 The capacity retention rate was only 64.71%, and after 2000 cycles, it was only 29.18 mAh g. -1 The capacity.

[0139] Figure 11 The composite materials prepared in Examples 4, 5, 6 and Comparative Example 1 were subjected to a reaction at 10 A g. -1 Cyclic performance graph at current density. (From...) Figure 11 As can be seen from Table 5, in Example 4, at 10 A g -1 After 1000 cycles at the current density, it has a capacity of 347.86 mAh g. -1 It exhibits reversible capacity with a capacity retention of 68.52%, and retains 319.70 mAh g after 8000 cycles. -1 The reversible capacity was maintained at 62.97%; Example 5 showed a capacity retention of 62.97% at 10 A g. -1 After 1000 cycles at the current density, it has a capacity of 694.86 mAh g. -1 It exhibits reversible capacity with a capacity retention rate of up to 96.52%, retaining 605.94 mAh g after 8000 cycles. -1 The reversible capacity above has a capacity retention rate of 84.17%; Example 6 at 10 A g -1After 1000 cycles at the current density, it only has 50.01 mAh g⁻¹. -1 The capacity retention rate was only 47.14%, and after 8000 cycles, it had 85.64 mAh g. -1 The reversible capacity was maintained at 80.72%; Comparative Example 1 at 10 A g - ¹After only 1000 cycles at current density, it only has 38.31 mAh g⁻¹ -1 The capacity.

[0140] Figure 12 The charge-discharge curves of the composite material prepared in Comparative Example 1 at different current densities are shown. Figure 12 The results show that Comparative Example 1 exhibits significant voltage polarization and a short reversible capacity plateau at low current densities. As the current density gradually increases, its performance deteriorates sharply; the characteristic alloying plateau of silicon rapidly becomes skewed, blurred, and eventually disappears completely, degenerating into a skewed straight line. The specific charge capacity of Comparative Example 1 decreases significantly with increasing current density, reaching a minimum at 0.2 A g. -1 At the given current density, the initial charge specific capacity of each sample was as follows: Example 4 (1484.14 mAh g⁻¹) -1 Example 5 (1819.52 mAh g) -1 Example 6 (1981.68 mAh g) -1 Comparative Example 1 (1745.54 mAh g) -1 When the current density increases to 0.5 A g -1 At that time, the capacities were 1321.97, 1626.04, 1626.04, and 1109.14 mAh g, respectively. -1 ;1 A g -1 At that time, the values ​​were 1116.67, 1417.03, 1417.63, and 922.32 mAh g. -1 ;2 A g -1 At that time, the values ​​were 932.84, 1284.11, 1136.47, and 750.93 mAh g. -1 5 A g -1 At that time, the values ​​were 788.55, 1016.26, 788.55, and 504.58 mAh g. -1 When the current density is further increased to 10 A g -1 At that time, Example 5 (784.31 mAh g) -1 The capacity remains high, while Example 6 (129.87 mAh g) still maintains a high capacity. -1 ) and Comparative Example 1 (113.94 mAh g) -1The capacity of Example 5 (489.95 mAh g⁻¹) decreased sharply at the limiting rate of 20 A g⁻¹. -1 ) exhibited excellent limiting rate performance, while Example 6 (22.94 mAh g) -1 ) and Comparative Example 1 (13.60 mAh g) -1 The capacity of Example 5 was almost completely lost, indicating that Example 5 has more stable electrochemical performance under rapid charge and discharge conditions.

[0141] Figure 13 The graphs show the charge-discharge curves of the composite material prepared in Example 5 at different current densities. Figure 13 Example 5 was demonstrated in 0.2-20 Ag. -1 Typical charge-discharge curves at current densities. As shown in the figure, at 0.5 A g... -1 At current density, its discharge curve exhibits a long and flat voltage plateau at approximately 0.15 V, a characteristic of the silicon-lithium alloying reaction, directly contributing to its high 1850 mAh g⁻¹. - The reversible specific capacity is above ¹; the dealloying plateau corresponding to the charging curve is located at approximately 0.4V, with a small voltage hysteresis between it and the discharging plateau, indicating low electrode polarization and good reaction kinetics. The iron-based silicon-phosphorus composite material of this invention exhibits a specific capacity of 0.2 A g. - ¹ to 20 A g - ¹ It exhibits excellent rate performance over a wide current density range. At 0.2 A g - At low rates, Example 5 exhibits the highest initial charge specific capacity of 1666.76 mAh g⁻¹. -1 mAh g - ¹,;in 0.5 A g - ¹When, Example 5 (1481.25 mAh g) - The advantages of ¹) become even more apparent when the current density reaches 1 A g. -1 At that time, Example 5 (1287.78 mAh g) - ¹) and (1475.01 mAh g) - ¹) It still exhibits excellent high-rate capacity retention capability; at 2 A g -1 At the specified current density, the specific charge capacity of Example 5 is 1169.01 mAh g. - ¹, at 5 A g -1 At high magnification, Example 5 (927.78 mAh g) -1 It exhibits optimal capacity retention when the current density is further increased to 10 A g. -1 At that time, Example 5 (709.79 mAh g) -1It still maintains excellent performance at 20 A g -1 At the limiting current density, Example 5 (439.03 mAh g) -1 It exhibits excellent performance at maximum rate.

[0142] Figure 14 The graphs show the rate performance of the composite materials prepared in Examples 4, 5, and 6, and Comparative Example 1, under different current densities. Figure 14 It can be seen that the iron-based silicon-phosphorus composite material of the present invention is effective at 0.2 A g. -1 Up to 20 A g -1 It exhibits excellent rate performance over a wide current density range. At 0.2 A g -1 At low charging rates, Example 6 exhibits the highest initial charge specific capacity of 2068.76 mAh g. -1 The concentration in Example 5 was 1666.76 mAh g. -1 Maintain a high level. At 0.5 A g -1 At that time, Example 6 (1736.67 mAh g) -1 ) and Example 5 (1481.25 mAh g) -1 The advantages of ) are further demonstrated, while the comparative example 1 (1598.24 mAh g) -1 The current density began to show a significant capacity decay trend. When the current density reached 1 A g... -1 At that time, Example 5 (1287.78 mAh g) -1 ) and Example 6 (1475.01 mAh g) -1 It still exhibits superior high-rate capacity retention capability, significantly better than Example 4 (1089.95 mAh g). -1 ) and Comparative Example 1 (1287.78 mAh g) -1 ). In 2 A g -1 At current density, Example 5 (1169.01 mAh g) -1 ) and Example 6 (1169.01 mAh g) -1 They are neck and neck, while the comparative example 1 (1100.28 mAhg) -1 A clear disadvantage has emerged. (In 5 A g) -1 At high magnification, Example 5 (927.78 mAh g) -1 It exhibited the best capacity retention capability, significantly higher than Example 4 (749.86 mAh g). -1 Example 6 (868.06 mAh g) -1 ) and Comparative Example 1 (749.86 mAh g) -1When the current density is further increased to 10 A g -1 At that time, Example 5 (709.79 mAh g) -1 ) still maintains excellent performance, while Example 6 (162.78 mAh g) -1 ) and Comparative Example 1 (185.53 mAh g) -1 A sharp decline occurs. At 20 A g -1 At the limiting current density, Example 5 (439.03 mAh g) -1 It exhibits superior limiting rate performance, while Example 6 and Comparative Example 1 both have only 32.78 mAh g⁻¹ remaining. -1 Its capacity is almost completely rendered unusable.

[0143] Figure 15 The composite material prepared in Example 4 was at 0.2 mV s -1 The CV curve at the scan rate. This CV curve shows that the negative electrode of Example 4 exhibits significant reduction peaks near 0.28 V and 0.58 V, while the reduction characteristics in the vicinity during the initial positive electrode (lithiation) are negligible. This corresponds to the reduction peaks of P and Si in the formation of Li3P and Li, respectively. x The alloying reactions that occur successively during the Si product process. During the initial negative electrode (lithiation) process, an oxidation peak appears around 0.34 V, which should be related to the crystalline / amorphous Li₂ process. x The phase transition from Si to amorphous Si is related; while the strong negative electrode characteristics near 0.58 and 1.10 V reflect a reversible structural evolution process, namely the transformation from Li3P to amorphous P.

[0144] Figure 16 The composite material prepared in Example 5 was at 0.2 mV s -1 The CV curve at the scan rate. This CV curve shows that the negative electrode of Example 5 exhibits significant reduction peaks near 0.28 V and 0.54 V, while the reduction characteristics in the vicinity during the initial positive electrode (lithiation) are negligible. This corresponds to the reduction peaks of P and Si in the formation of Li3P and Li, respectively. x The alloying reactions that occur successively during the Si product process. During the initial negative electrode (lithiation) process, an oxidation peak appears around 0.34 V, which should be related to the crystalline / amorphous Li₂ process. xThe phase transition from Si to amorphous Si is related; while the strong negative electrode features near 0.58 and 1.10 V reflect a reversible structural evolution process, namely, the transformation from Li3P to amorphous P. From the second cycle onwards, the subsequent CV curves almost completely overlap, and the peak positions, peak shapes, and peak intensities of the oxidation and reduction peaks highly coincide in multiple cycles. Compared with Example 4, the peak current (peak height) of Example 5 is significantly larger at the same scan rate.

[0145] Figure 17 The composite material prepared in Example 6 was at 0.2 mV s -1 The CV curve at the scan rate. This CV curve shows that the negative electrode of Example 6 exhibits significant reduction peaks near 0.28 V and 0.58 V, while the reduction characteristics in the vicinity during the initial positive electrode (lithiation) are negligible. This corresponds to the reduction peaks of P and Si in the formation of Li3P and Li, respectively. x The alloying reactions that occur successively during the Si product process. During the initial negative electrode (lithiation) process, the reduction characteristics in its vicinity are negligible, which should be attributed to the crystalline / amorphous Li... x The phase transition from Si to amorphous Si is related; while the strong negative electrode characteristics near 0.58 and 1.10 V reflect a reversible structural evolution process, namely the transformation from Li3P to amorphous P.

[0146] Figure 18 The composite material prepared for Comparative Example 1 was tested at 0.2 mV s. -1 CV curves at different scan rates. Compared to Examples 4, 5, and 6, in the absence of an Fe matrix, the negative electrode of Comparative Example 1 exhibits a significant reduction peak near 0.57 V, while the reduction characteristics near 0.14 V are negligible during the initial positive electrode (lithiation) process. This corresponds to the reduction peaks of P and Si in the formation of Li3P and Li, respectively. x The alloying reactions that occur successively during the Si product process. During the initial negative electrode (lithiation) process, a significant oxidation peak appears around 0.34 V, which should be related to the crystalline / amorphous Li₂ process. x The phase transition from Si to amorphous Si is related; while the strong negative electrode characteristics near 0.51 and 1.10 V reflect a reversible structural evolution process, namely the transformation from Li3P to amorphous P.

[0147] Figure 19 The image shows the CV curves of the composite material prepared in Example 5 at different scan rates. Figure 19 As shown in the CV plot, the negative electrode of Example 5 exhibits significant reduction peaks near 0.28 V and 0.54 V, while the reduction characteristics in the vicinity are negligible during the initial positive electrode (lithiation) process. This corresponds to the reduction peaks of P and Si in the formation of Li3P and Li, respectively.x The alloying reactions that occur successively during the Si product process. During the initial negative electrode (lithiation) process, an oxidation peak appears around 0.34 V, which should be related to the crystalline / amorphous Li₂ process. x The phase transition from Si to amorphous Si is related; while the strong negative electrode characteristics near 0.58 and 1.10 V reflect a reversible structural evolution process, namely, the transformation from Li3P to amorphous P. The peak currents of all characteristic redox peaks (silicon-lithium alloying / dealloying peaks) systematically increase with increasing scan rate, and the peak positions shift regularly, even at up to 1.0 mV s. -1 At a faster scan rate, the CV curve still maintained a clear silicon characteristic redox peak shape without serious deformation or disappearance. Compared with Comparative Example 1, at the same scan rate, the peak current (peak height) of Example 5 was significantly larger.

[0148] Figure 20 The CV curves of the composite material prepared in Comparative Example 1 at different scan rates are shown. Compared with Examples 4, 5, and 6, in the absence of an Fe matrix, the negative electrode of Comparative Example 1 exhibits a significant reduction peak near 0.57 V, while the reduction characteristic near 0.14 V is negligible during the first positive electrode (lithiation) process. This corresponds to the reduction peaks of P and Si in the formation of Li3P and Li, respectively. x The alloying reactions that occur successively during the Si product process. During the initial negative electrode (lithiation) process, a significant oxidation peak appears around 0.34 V, which should be related to the crystalline / amorphous Li₂ process. x The phase transition from Si to amorphous Si is related; while the strong negative electrode characteristics near 0.51 and 1.10 V reflect a reversible structural evolution process, namely, the transformation from Li3P to amorphous P. As shown in the figure, the peak shape of Comparative Example 1 is broad and diffuse, rapidly deteriorating and becoming blurred with increasing scan rate. At high scan rates, the peak almost disappears, and the peak shape broadens and deteriorates rapidly with scan rate, possibly indicating a large charge transfer resistance and a slow lithium-ion solid-phase diffusion rate. The voltage gap (ΔEp) between the cathode peak and the anode peak is very large, and the increase of ΔEp with increasing scan rate is also extremely significant. This is a direct manifestation of huge ion / electron transport resistance and slow reaction kinetics. At the same scan rate, the peak current (Ip) of Comparative Example 1 is much lower than that of Example 5.

[0149] Figure 21 This is a linear fit graph showing the peak current versus the square root of the scan rate for the composite materials prepared in Example 5 and Comparative Example 1 during CV testing. Figure 21As shown, for the cathode peaks (Peak 1, 2) representing the silicon-lithium alloying process, the absolute slope values ​​of Example 5 are 16% to 112% higher than those of Comparative Example 1. For the anode peaks (Peak 3, 4) representing the dealloying process, the absolute slope values ​​of Example 5 are 26% to 133% higher than those of Comparative Example 1. For all four characteristic peaks, the absolute slope values ​​of the fitted lines in Example 5 are significantly greater than those in Comparative Example 1, and the lithium-ion diffusion coefficient (D) of Example 5 is also significantly higher. - Li + The result was significantly higher than that of the control group 1, and even improved by more than an order of magnitude in key reaction steps.

[0150] Figure 22 This is a SEM image of the composite material prepared in Example 5. The iron-based silicon-phosphorus anode material prepared in this invention has a small particle size and uniform dispersion properties. Figure 22 (b)), and exhibits a relatively low degree of cohesion ( Figure 22 (df)). It is worth mentioning that the introduction of an appropriate amount of iron will significantly reduce the crystallinity of the composite material ( Figure 22 (gh)), and can ensure the uniform distribution of different elements in the microstructure ( Figure 22 (ij)).

[0151] Figure 23 The full cell assembled from the composite material prepared in Example 5 was tested at 0.1 A g. -1 Cycling performance at current density. The full cell assembled from the iron-based silicon-phosphorus composite material of this invention and a commercially available cathode operates at 0.1 A g. -1 and 0.2 Ag -1 It exhibits good cycling stability at all current densities. At 0.1 A g... -1 At the given current density, the initial discharge specific capacity of the full cell in Example 5 was 175.29 mAh g⁻¹. -1 The initial coulomb efficiency was 62.84%; after 100 cycles, the capacity was 128.06 mAhg. -1 The capacity retention rate was 73.05%; after 300 cycles, the capacity was 105.98 mAh g. -1 The capacity retention rate was 62.84%.

[0152] Figure 24 The full cell assembled from the composite material prepared in Example 5 was tested at 0.2 A g. -1 Cycling performance at current density. The full cell assembled from the iron-based silicon-phosphorus composite material of this invention and a commercially available cathode performs well at 0.2 A g. -1 At the given current density, the initial discharge specific capacity of the full cell in Example 5 was 167.87 mAh g⁻¹. -1The initial coulomb efficiency improved to 65.26%; after 100 cycles, the capacity was 125.14 mAh g. -1 The capacity retention rate was 74.54%; after 300 cycles, the capacity remained at 102.56 mAh g. -1 The capacity retention rate was 61.09%, and after 700 cycles, the capacity remained at 83.71 mAh g. -1 The capacity retention rate was 49.86%.

[0153] Figure 25 The full cell assembled from the composite material prepared in Example 5 was tested at 0.1 A g. -1 Charge-discharge curves at current density. A distinct voltage plateau is observed near 3.8 V, corresponding to nickel oxidation and lithium-ion extraction in NCM811. The initial charge capacity determines the total amount of lithium extracted from the cathode. As the number of cycles increases (from 1 to 300), the horizontal length (capacity) of the charge-discharge curve gradually shortens, but the decay rate is relatively slow, indicating that the full cell capacity gradually decreases, but the decay rate is well controlled. The voltage gap (ΔV) between the charge-discharge curves is observed. This gap only slightly increases with cycling. The full cell assembled from the iron-based silicon-phosphorus composite material of this invention and a commercially available cathode achieves a capacity of 0.1 A g. -1 It exhibits good cycling stability at current densities of 0.1 A g. -1 At the given current density, the initial discharge specific capacity of the full cell in Example 5 was 175.29 mAh g⁻¹. -1 The initial coulomb efficiency was 62.84%; after 50 cycles, the capacity remained at 139.33 mAh g⁻¹. -1 The capacity retention rate was 79.48%; after 100 cycles, the capacity was 128.06 mAh g. -1 The capacity retention rate was 73.05%; after 300 cycles, the capacity was 105.98 mAh g. -1 The capacity retention rate was 60.45%.

[0154] Figure 26 The full cell assembled from the composite material prepared in Example 5 was tested at 0.2 A g. -1 Charge-discharge curves at current density. The full cell assembled from the iron-based silicon-phosphorus composite material of this invention and a commercially available cathode operates at 0.2 A g. -1 At the given current density, the initial discharge specific capacity of the full cell in Example 5 was 167.87 mAh g⁻¹. -1 The coulomb efficiency improved to 65.26% in the first cycle; after 50 cycles, the capacity remained at 137.05 mAh g. -1The capacity retention rate was 81.64%; after 100 cycles, the capacity was 125.14 mAh g. -1 The capacity retention rate was 74.54%; after 300 cycles, the capacity remained at 102.56 mAh g. -1 The capacity retention rate was 61.09%, and after 700 cycles, the capacity remained at 83.71 mAh g. -1 The capacity retention rate was 49.86%. After 700 cycles, the characteristic charge-discharge voltage plateau (~3.7 V) of NCM811 remained clear and flat, with its shape and position almost identical to that of the first cycle. This indicates that the electrochemical reactions of the positive and negative electrode materials are highly reversible and the pathways are extremely stable. Before and after 700 cycles, the voltage gap between the charge-discharge curves increased only slightly, reflecting that the internal resistance of the entire cell increased negligibly, and the capacity showed a uniform and slow decreasing trend with the increase of the number of cycles.

[0155] Figure 27 The graph shows the rate performance of the full cell assembled from the composite material prepared in Example 5 at different current densities. The full cell assembled in Example 5 of this invention with a commercially available cathode performs at 0.04 A g. -1 Up to 1.0 A g -1 It exhibits excellent rate performance and capacity retention over a wide current density range. At 0.04 A g... -1 At low charging rates, the initial charge specific capacity of the full battery is as high as 285.14 mAh g. -1 When the current density is increased to 0.1 A g -1 At that time, the capacity remained at 152.36 mAh g. -1 It represents 53.4% ​​of the capacity at low rates; at 0.2 A g -1 The lower capacity is 140.06 mAh g. -1 (Retention rate 49.1%); at 0.4 A g -1 The lower capacity is 130.2 mAh g. -1 (Retention rate 45.7%); even at 1.0 Ag -1 Even at high rate, the full battery can still provide 122.66 mAh g. -1 The material exhibits a considerable capacity retention rate of up to 43.0%. This demonstrates that the material possesses excellent power characteristics and rapid charge transport dynamics in practical full-cell systems, enabling it to meet the demands of a wide range of applications, from slow energy storage to rapid charge and discharge.

[0156] Figure 28The graphs show the charge-discharge curves of the full cell assembled from the composite material prepared in Example 5 at different current densities. At low rates, the curves show the longest and flattest charge-discharge plateau (approximately 3.6-3.8 V), indicating the highest capacity and representing the maximum reversible capacity of this full cell system. The voltage plateau is clear, and polarization is minimal. As the current density increases from 0.04 A g... -1 Gradually increase to 1.0 Ag -1 The battery's discharge capacity gradually decreases, but even at its highest of 1.0 A g, it still maintains its capacity. -1 Under current, its charge-discharge curves still maintain a clear NCM811 voltage plateau; as the current increases, the voltage polarization between the charge-discharge curves gradually increases, but the growth trend is gradual, reaching 1.0 A g. -1 No severe distortion or breakage of the voltage plateau was observed; after a series of high-rate tests, the current density returned to 0.04 A g. -1 At that time, its charge-discharge curve was similar to that of 0.1 Ag. -1 The rate curves at these depths highly overlap. The full cell at 0.04 A g... -1 Up to 1.0 A g -1 It exhibits excellent rate performance and capacity retention over a wide current density range. At 0.04 A g... -1 At low charging rates, the initial charge specific capacity of the full battery is as high as 285.14 mAh g. -1 When the current density is increased to 0.1 A g -1 At that time, the capacity remained at 152.36 mAh g. -1 It represents 53.4% ​​of the capacity at low rates; at 0.2 A g -1 The lower capacity is 140.06 mAh g. -1 (Retention rate 49.1%); at 0.4 A g -1 The lower capacity is 130.2 mAh g. -1 (Retention rate 45.7%); even at 1.0 Ag -1 Even at high rate, the full battery can still provide 122.66 mAh g. -1 It has a considerable capacity and a retention rate of up to 43.0%.

[0157] Compared with existing technologies, in the iron-based silicon-phosphorus composite anode material of the present invention, the introduction of elemental iron induces microstructural disorder, reducing the lithium-ion diffusion barrier. At the same time, elemental iron and in-situ formed lithium phosphide provide abundant electron and ion transport pathways, respectively, and synergistically buffer the huge volume deformation of silicon anode during lithiation / delithiation processes, thereby effectively improving its electrochemical reversibility, cycle stability, and rate performance during lithium storage. The iron-based silicon-phosphorus composite anode material can be prepared by one-step / multi-step mechanical ball milling, and the corresponding material exhibits more uniform particle size and elemental distribution. Moreover, the raw material cost is low, and the material preparation process is simple; it can be scaled up for mass production.

[0158] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, it will be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An amorphous iron-based silicon-phosphorus composite anode material, characterized in that, The raw materials include elemental iron, elemental silicon, elemental phosphorus, and carbon materials. The molar ratio of silicon to phosphorus is 2:1 to 1:2, the molar ratio of silicon to iron is 8:1 to 1:2, and the mass ratio of the mixture of elemental iron, elemental silicon, and elemental phosphorus to carbon materials is 5:5 to 8:

2. The iron-based silicon-phosphorus composite anode material is prepared by one-step or multi-step mechanical ball milling.

2. The amorphous iron-based silicon-phosphorus composite anode material as described in claim 1, characterized in that, The iron is sourced from elemental iron powder or nano-iron powder; the silicon is sourced from elemental silicon powder or nano-silicon powder; the phosphorus is sourced from elemental phosphorus powder or nano-phosphorus powder; and the carbon material is conductive carbon black or carbon nanomaterial.

3. The amorphous iron-based silicon-phosphorus composite anode material as described in claim 1, characterized in that, The mass ratio of the mixture of silicon, phosphorus, and iron to carbon material is 5:5, 6:4, 7:3, or 8:2; the purity of silicon is 99.9% and the particle size is 50-500 nm; the purity of phosphorus is 98-99.99%.

4. A method for preparing an amorphous iron-based silicon-phosphorus composite anode material as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Weigh out elemental silicon, elemental phosphorus, elemental iron, and carbon materials; (2) Weigh the grinding balls; (3) The iron-based silicon-phosphorus composite anode material is prepared by one or more steps of mechanical ball milling.

5. The method for preparing the amorphous iron-based silicon-phosphorus composite anode material as described in claim 4, characterized in that, The one-step mechanical ball milling method in step (3) is as follows: First, the raw materials weighed in step (1) and the grinding balls weighed in step (2) are transferred to a ball milling jar; then, in argon gas, the ball milling jar is assembled, and the iron, silicon, phosphorus and carbon materials in step (1) are mixed and ground using a ball mill. First, preliminary physical mixing is carried out at speeds of 100~200 rpm and 200~300 rpm for 8~24 h respectively, followed by high-energy ball milling at speeds of 300~600 rpm for 12~48 h; the preliminary physical mixing and high-energy ball milling are repeated at least twice to obtain the material.

6. The method for preparing the amorphous iron-based silicon-phosphorus composite anode material as described in claim 4, characterized in that, The multi-step mechanical ball milling method in step (3) is as follows: First, the iron, silicon, and phosphorus elements weighed in step (1) and the grinding balls weighed in step (2) are transferred to a ball milling jar and assembled in an argon atmosphere. Then, gradient ball milling technology is used to first perform preliminary physical mixing at speeds of 100-200 rpm and 200-300 rpm for 8-24 h, respectively. Then, high-energy ball milling is performed at speeds of 300-600 rpm for 12-48 h. The above ball milling steps are repeated at least twice to obtain an iron / silicon / phosphorus composite anode material. Then, the carbon material weighed in step (1) and the prepared iron / silicon / phosphorus composite anode material are added to a ball mill jar and sealed and assembled in an argon atmosphere. Finally, gradient ball milling technology is used to first perform preliminary physical mixing at speeds of 100~200 rpm and 200~300 rpm for 8~24 h, and then perform high-energy ball milling at speeds of 300~600 rpm for 12~48 h. The above preliminary physical mixing and high-energy ball milling are repeated at least twice to obtain an amorphous iron-based silicon-phosphorus composite anode material.

7. The method for preparing the amorphous iron-based silicon-phosphorus composite anode material as described in claim 5 or 6, characterized in that, The mass ratio of the grinding balls to the raw materials is 20:1 to 50:1; the grinding balls are made of stainless steel beads of different sizes with diameters of 2 to 10 mm; the protective atmosphere is one or more of the following gases: argon, nitrogen, helium, argon and hydrogen, or a mixture of nitrogen and hydrogen; in the process of high-energy ball milling at 100 to 200 rpm for 8 to 24 hours, high-energy ball milling at 100, 150, or 200 rpm for 12 to 18 hours is selected; in the process of high-energy ball milling at 200 to 300 rpm for 8 to 24 hours, high-energy ball milling at 200, 250, or 300 rpm for 12 to 18 hours is selected; in the process of high-energy ball milling at 300 to 600 rpm for 12 to 48 hours, high-energy ball milling at 350, 400, 450, or 500 rpm for 24 to 36 hours is selected.

8. The method for preparing the amorphous iron-based silicon-phosphorus composite anode material as described in claim 7, characterized in that, The mass ratio of the grinding balls to the raw materials is 20:1, 30:1, or 40:1; three types of stainless steel balls with sizes of 2 mm, 3 mm, and 5 mm are selected and mixed, and the mass ratio of the three types of stainless steel balls is 1:1:

1.

9. A lithium-ion half-cell, characterized in that, Its preparation method includes the following steps: S1. Weigh the iron-based silicon-phosphorus composite material according to any one of claims 1-3 with conductive carbon black and binder in a mass ratio of m:n:l to obtain a mixture, wherein m is 60~80 wt.%, n is 10~30 wt.%, l is 10~30 wt.%, and the mixture is uniformly dispersed in deionized water to prepare an electrode slurry; S2. The slurry obtained in step S1 is uniformly coated onto copper foil and vacuum dried at 60~70 ℃ for 10~15 hours. Then the copper foil is cut into circular electrode sheets for later use. S3. Using the electrode obtained in step S2 as the negative electrode and the lithium metal sheet as the counter electrode, an electrolyte is added and the cells are assembled into a half-cell. The electrolyte is 1.0 M LiPF6 in DMC:EC:EMC = 1:1:1 Vol% with 10% FEC and 2% VC.

10. A lithium-ion full battery, characterized in that, Its preparation method includes the following steps: S'1. Weigh the iron-based silicon-phosphorus composite material according to any one of claims 1-3 with conductive carbon black and binder in a mass ratio of m:n:l, where m is 60~80 wt.%, n is 10~30 wt.%, and l is 10~30 wt.%, and uniformly disperse the mixture in deionized water to prepare an electrode slurry with stable properties and uniform dispersion. S'2. The slurry obtained in step S'1 is uniformly coated onto copper foil and vacuum dried at 60~70 ℃ for 10~15 hours. Then the copper foil is cut into circular electrode sheets for later use. S'3. Weigh the positive electrode active material, conductive carbon black, and binder according to the mass ratio of m:n:l, where m is 60~80 wt.%, n is 10~30 wt.%, and l is 10~30 wt.%. Disperse the mixture uniformly in N-methylpyrrolidone solvent to prepare the electrode slurry. S'4. The slurry obtained in step S'3 is uniformly coated onto aluminum foil, dried at 90~120 ℃ for 10~15 hours, and then the aluminum foil is cut into circular electrode sheets for later use. S'5. Physically pre-lithiate the electrode obtained in step S'2. The physical pre-lithiation involves physically bonding the negative electrode with lithium metal in an appropriate amount of electrolyte while applying an external pressure of 0.2~1.0 MPa for 10~30 minutes. S'6. Using the electrode obtained in step S'5 as the negative electrode and the electrode obtained in step S'4 as the counter electrode, add electrolyte and assemble into a full cell. The electrolyte is 1.0 M LiPF6 in EC:DMC:EMC = 3:4:3 Vol% with 10% FEC and 2% VC, or 1.0 M LiPF6 in DMC:EC:EMC = 1:1:1 Vol% with 10% FEC and 2% VC, or 1.0 M LiPF6 in EC:EMC = 3:7 Vol% with 5% FEC, 2% VC, and 3% TEOSCN, or 1.0 M LiPF6 in EC:DMC:EMC = 1:1:1 Vol% with 10% FEC and 1-2% MBA, or 1.2 M LiFSI with 0.05 M LiDFOB in DME:HFE:FEC = 3:6:1 Vol%.

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