A phosphorus-based doped modified electrode material, a dry-process electrode sheet, its preparation method and application

Abstract

This invention provides a phosphorus-based doped modified electrode material, a dry-process electrode sheet, its preparation method, and its applications, relating to the field of electrode material preparation technology. The preparation method of the phosphorus-based doped modified electrode material provided by this invention includes the following steps: mixing a phosphorus-based material, a carbon material, and a dopant material; and performing high-energy ball milling under a protective atmosphere to obtain the phosphorus-based doped modified electrode material; the high-energy ball milling speed is 100–1000 cpm. This invention utilizes the synergistic regulation of carbon coating and doping modification to control the phosphorus-based electrode material, achieving a significant improvement in its electrochemical performance.

Description

Technical Field

[0001] This invention relates to the field of electrode material preparation technology, specifically to a phosphorus-based doped modified electrode material, a dry electrode sheet, its preparation method, and its application. Background Technology

[0002] Compared to traditional lead-acid battery / supercapacitor hybrid power supplies, novel lithium-ion capacitors (LICs) offer advantages such as long cycle life and low self-discharge, making them widely applicable in applications such as emergency train start-stop, large machinery, backup power, and instantaneous high-power transmission. However, currently commercially viable electrode materials, such as graphite anodes, suffer from low reversible capacity (372 mAh / g) and low lithiation potential (0.1 V vs. Li). + The limitations of lithium-ion batteries (Li₂O₃) and slow kinetics prevent them from meeting the current development needs of high-energy, high-power energy storage devices. Lithium-ion batteries (LICs) innovatively combine the negative electrode of a lithium-ion battery and the positive electrode of a supercapacitor, potentially solving the problems of low capacity of the supercapacitor's positive electrode and poor rate performance of the lithium-ion battery's negative electrode. This can significantly improve the energy density and power density of the hybrid device, achieving the goal of high-energy, high-power (dual-high) energy storage devices. In the aforementioned battery-capacitor hybrid energy storage device system, the battery component undergoing the Faraday reaction and the capacitor component undergoing the double-layer energy storage process work synergistically, resulting in a significant improvement in energy density and power density. However, currently, no device can achieve an energy density of 150 Wh / kg⁻¹. -1 and power density 150kWkg -1 The reported dual-device system is far from meeting the performance requirements of electromagnetic drive devices for energy storage devices.

[0003] Phosphorus-based materials are known to have significantly improved specific capacity (approximately 2596 mAh / g and approximately 6000 mAh / cm³). 3 And with Li + Li can be formed at high potentials (approximately 0.7V) during electrochemical interactions. x P(x≤3) compounds effectively suppress the formation of lithium dendrites. These advantages make phosphorus-based materials a promising electrode candidate for high-energy-density, high-power energy storage devices. However, phosphorus-based materials themselves have extremely poor conductivity. For example, black phosphorus is a semiconductor material with a direct band gap, which limits its electron transfer capability. Furthermore, lithium intercalation in phosphorus-based materials is accompanied by a volume expansion of approximately 300%. These drawbacks further restrict the practical application of phosphorus-based materials in energy storage scenarios. Improving the application of phosphorus-based materials in high-specific-energy, high-power energy storage devices is a core problem that needs to be solved. Summary of the Invention

[0004] The purpose of this invention is to provide a phosphorus-based doped modified electrode material, a dry electrode sheet, its preparation method and application. The phosphorus-based doped modified electrode material prepared by this invention effectively solves the problems of poor conductivity and structural expansion of phosphorus-based materials.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a phosphorus-based doped modified electrode material, comprising the following steps:

[0007] Phosphorus-based materials, carbon materials, and doped materials are mixed and subjected to high-energy ball milling in a protective atmosphere to obtain phosphorus-based doped modified electrode materials; the high-energy ball milling speed is 100-1000 cpm.

[0008] Preferably, the phosphorus-based material includes one or more of white phosphorus, red phosphorus, and black phosphorus.

[0009] Preferably, the carbon material includes one or more of flake graphite, expanded graphite, graphene, and carbon nanotubes.

[0010] Preferably, the doping material comprises a metallic element and / or a non-metallic element; the metallic element comprises one or more of antimony, titanium, and bismuth; and the non-metallic element comprises one or more of boron and nitrogen.

[0011] Preferably, the mass ratio of the phosphorus-based material, carbon material and doped material is 50-90:10-20:5-20.

[0012] Preferably, the high-energy ball milling time is 12 to 240 hours.

[0013] The present invention provides a phosphorus-based doped modified electrode material prepared by the preparation method described in the above technical solution.

[0014] This invention provides a dry electrode sheet, using the phosphorus-based doped modified electrode material described in the above technical solution as the active component.

[0015] This invention provides a method for preparing a dry electrode sheet, comprising the following steps:

[0016] An electrode mixture is obtained by mixing an active component, conductive carbon, a binder, and a dispersant; the active component is the phosphorus-based doped modified electrode material described in the above technical solution.

[0017] The electrode mixture is repeatedly rolled to the target thickness, and then the resulting dry electrode is pressed onto the current collector and dried to obtain a dry electrode sheet.

[0018] This invention provides the application of the phosphorus-based doped modified electrode material described in the above technical solution, the dry electrode sheet described in the above technical solution, or the dry electrode sheet prepared by the preparation method described in the above technical solution in lithium-ion batteries or lithium-ion capacitors.

[0019] This invention provides a method for preparing phosphorus-based doped modified electrode materials. This invention ingeniously achieves carbon coating and doping modification of phosphorus-based materials through a one-step high-energy ball milling method. The resulting phosphorus-based doped modified electrode material exhibits improved reversible capacity, extended cycle life, and accelerated ion transport, effectively solving the problem of irreversible damage after lithium intercalation in expansion-type electrode materials. Based on the fact that the doping component can reduce the band gap of the host electrode material and stabilize its interface structure, the conductivity and cycle stability of the phosphorus-based doped modified electrode material prepared by this invention are improved. Further assembly of the full cell results in high energy density and high power density, and achieves a long cycle life.

[0020] The present invention improves the structural stability of phosphorus-based materials through the synergistic effect of carbon coating and doping modification. For example, in the case of black phosphorus electrode materials, Sb metal doping can reduce the band gap of black phosphorus, thereby promoting electron transfer. Simultaneously, carbon coating increases the conductivity and structural stability of the black phosphorus interface, effectively mitigating the volume expansion after lithium intercalation. This invention achieves both carbon coating and doping modification of phosphorus-based materials simultaneously through a one-step high-energy ball milling method, resulting in a phosphorus-based composite electrode material with stable cycle structure.

[0021] In this invention, the phosphorus-based material, carbon material, and doped material can achieve atomic-level bonding, overcome the interfacial reaction barrier to undergo chemical reactions, and form stable new chemical bonds, which greatly improves the structural stability of the phosphorus-based material during charge-discharge cycles.

[0022] This invention utilizes carbon coating and doping modification to synergistically regulate phosphorus-based electrode materials, achieving a significant improvement in their electrochemical performance. Furthermore, the preparation process provided by this invention is simple, requires minimal equipment investment, and is easily scalable for large-scale industrial production. Attached Figure Description

[0023] Figure 1 SEM images of the electrode materials prepared for RP, Examples 1-5 and Comparative Examples 1-2;

[0024] Figure 2 The XRD patterns of the electrode materials prepared in Examples 1-5 and Comparative Examples 1-2 are shown.

[0025] Figure 3 Raman spectra of the electrode materials prepared in Examples 1-5 and Comparative Examples 1-2;

[0026] Figure 4Charge-discharge curves of CR2025 coin cells assembled with dry electrode sheets corresponding to Examples 1-6 and Comparative Examples 1-2;

[0027] Figure 5 Electrochemical performance characterization of the lithium-ion full cell assembled with Ti-N@BP / C anode and lithium iron phosphate cathode in Example 5;

[0028] Figure 6 This is a schematic diagram illustrating the working principle of assembling a lithium-ion battery according to the present invention. Detailed Implementation

[0029] This invention provides a method for preparing a phosphorus-based doped modified electrode material, comprising the following steps:

[0030] Phosphorus-based materials, carbon materials, and doped materials are mixed and subjected to high-energy ball milling in a protective atmosphere to obtain phosphorus-based doped modified electrode materials; the high-energy ball milling speed is 100-1000 cpm.

[0031] Unless otherwise specified, all raw materials used in this invention are commercially available products well known to those skilled in the art.

[0032] In this invention, the phosphorus-based material preferably includes one or more of white phosphorus, red phosphorus, and black phosphorus, more preferably red phosphorus. In this invention, the red phosphorus is stable under air conditions and is inexpensive.

[0033] In this invention, the carbon material preferably includes one or more of flake graphite, expanded graphite, graphene and carbon nanotubes, and more preferably carbon nanotubes.

[0034] In this invention, the doping material preferably comprises a metallic element and / or a non-metallic element; the metallic element preferably comprises one or more of antimony (Sb), titanium (Ti), and bismuth (Bi); the non-metallic element preferably comprises one or more of boron (B) and nitrogen (N). In a specific embodiment of this invention, the doping material preferably comprises one or more of P3N5, Sb, TiO2, and Ti, and more preferably Ti and P3N5.

[0035] In this invention, the preferred mass ratio of the phosphorus-based material, carbon material, and dopant material is 50–90:10–20:5–20, more preferably 65–75:20–30:1–10. This invention does not impose any particular limitation on the particle size of the phosphorus-based material, carbon material, and dopant material; powders well-known to those skilled in the art can be used.

[0036] In this invention, the protective atmosphere is preferably argon (Ar). In this invention, the rotational speed of the high-energy ball mill is 100–1000 cpm, preferably 875 cpm. In this invention, the high-energy ball mill uses a vibratory ball mill, and its rotational speed is measured in the number of figure-eight revolutions per minute. In this invention, the high-energy ball milling time is preferably 12–240 hours, more preferably 24–36 hours. In this invention, the ball-to-material ratio of the high-energy ball mill is preferably 10–50:1, more preferably 10–20:1. In this invention, the jar and grinding balls used in the high-energy ball mill are preferably made of stainless steel; the particle size of the grinding balls is preferably 5–25 mm, more preferably a single diameter of 5 mm.

[0037] This invention employs high-energy ball milling, utilizing its mechanical energy to achieve atomic-level uniform mixing of phosphorus-based materials, carbon materials, and doped materials. Simultaneously, the immense shear and frictional forces generated by high-energy ball milling create high temperature and pressure in localized areas of the material, promoting the direct transformation of amorphous red phosphorus into black phosphorus crystals. This facilitates a strong chemical bond between the phosphorus and carbon materials and doped materials, overcoming interfacial reaction barriers and forming stable new chemical bonds (such as PC, Sb-P, Ti-P). This significantly improves the structural stability of phosphorus-based materials during charge-discharge cycles.

[0038] This invention provides a phosphorus-based doped modified electrode material prepared by the preparation method described above. In this invention, the phosphorus-based doped modified electrode material exhibits an overall irregular powder morphology; the phosphorus-based doped modified electrode material comprises a phosphorus-based material, a carbon material, and a dopant material; the phosphorus-based material, carbon material, and dopant material are uniformly mixed, and a portion of the carbon material forms a coating layer on the surface of the phosphorus-based material. In this invention, the dopant material is preferably uniformly distributed within and on the surface of the phosphorus-based doped modified electrode material. In this invention, the thickness of the coating layer is preferably in the range of 1–20 μm. In a specific embodiment of this invention, the phosphorus-based doped modified electrode material includes nitrogen; the mass content of the nitrogen is less than 10%.

[0039] The phosphorus-based doped modified electrode material prepared by this invention exhibits stable structure and high specific capacitance, effectively solving the problems of poor conductivity of phosphorus-based materials and the large volume expansion associated with lithiation. In this invention, the carbon material in the coating layer improves the conductivity at the interface of the phosphorus-based material, while the internal doping material alters the band structure of the phosphorus-based semiconductor, jointly improving the overall conductivity of the phosphorus-based doped modified electrode material. This results in excellent cycle performance and rate performance of the phosphorus-based doped modified electrode material.

[0040] This invention provides a dry-process electrode sheet, using the phosphorus-doped modified electrode material described in the above-mentioned technical solution as the active component. In this invention, the dry-process electrode sheet includes a current collector and an electrode material attached to the current collector; the active component of the electrode material includes the phosphorus-doped modified electrode material. In this invention, the content of the active component in the dry-process electrode sheet is preferably 60–90 wt%, more preferably 75–85 wt%.

[0041] This invention provides a method for preparing a dry electrode sheet, comprising the following steps:

[0042] An electrode mixture is obtained by mixing an active component, conductive carbon, a binder, and a dispersant; the active component is the phosphorus-based doped modified electrode material described in the above technical solution.

[0043] The electrode mixture is repeatedly rolled to the target thickness, and then the resulting dry electrode is pressed onto the current collector and dried to obtain a dry electrode sheet.

[0044] This invention mixes an active component, conductive carbon, a binder, and a dispersant to obtain an electrode mixture. In this invention, the active component is the phosphorus-doped modified electrode material described in the above-mentioned technical solution. In this invention, the conductive carbon preferably includes one or more of Ketjen Black, Super C45, and Super C55; the binder is preferably polytetrafluoroethylene (PTFE); and the dispersant is preferably isopropanol. In this invention, the mass ratio of the active component, conductive carbon, and binder is preferably 6.0–9.5:0.5–2:0.5–2, more preferably 8:1:1. In this invention, the solid content of the electrode mixture is preferably 55–65%, more preferably 60%.

[0045] In this invention, the mixing of the active component, conductive carbon, binder, and dispersant is preferably dry mixing. In a specific embodiment of this invention, the dry mixing includes: heating and stirring the active component, conductive carbon, and binder in a dispersant, and then grinding after the dispersant has completely evaporated. In this invention, the heating and stirring method is preferably magnetic stirring, the rotation speed is preferably 100-500 rpm, the heating and stirring temperature is preferably 50-90°C, and the heating and stirring time is preferably 10 min-2 h.

[0046] In a specific embodiment of the present invention, the electrode mixture exhibits a state similar to modeling clay.

[0047] After obtaining the electrode mixture, the present invention repeatedly rolls the electrode mixture to the target thickness, then presses the resulting dry electrode onto the current collector and performs a drying process to obtain a dry electrode sheet. In the present invention, the repeated rolling preferably includes: sequentially rolling the electrode mixture to heights of 20 mm, 15 mm, 10 mm, 5 mm, and 1 mm, rolling at least twice at each height. In the present invention, the current collector preferably includes an aluminum current collector, a copper current collector, nickel foam, or carbon cloth. In the present invention, the areal loading of the electrode mixture in the dry electrode sheet is preferably 0.5–2.5 g·cm³. -2 More preferably 1-2 g·cm³ -2 In this invention, the drying temperature is preferably 50–120°C, more preferably 60–100°C; the drying time is preferably 2–12 hours, more preferably 8–10 hours. In this invention, the drying process is preferably vacuum drying. In a specific embodiment of this invention, drying is performed at 60°C for 12 hours in a vacuum drying oven. The purpose of this drying method is to remove residual solvent from the dry electrode sheet without causing aging of the binder.

[0048] This invention provides the application of the phosphorus-based doped modified electrode material described in the above technical solution, the dry electrode sheet described in the above technical solution, or the dry electrode sheet prepared by the preparation method described in the above technical solution in lithium-ion batteries or lithium-ion capacitors.

[0049] In this invention, the method for preparing the lithium-ion battery preferably includes the following steps:

[0050] A lithium sheet, a first separator, a negative electrode, a second separator, and a positive electrode are sequentially stacked, encapsulated, and then an electrolyte is added to obtain a lithium-ion battery; the negative electrode is the dry electrode sheet described in the above technical solution or the dry electrode sheet prepared by the preparation method described in the above technical solution.

[0051] In this invention, the first diaphragm is preferably made of polypropylene microporous membrane; the second diaphragm is preferably made of polypropylene microporous membrane.

[0052] In this invention, the positive electrode is preferably a lithium iron phosphate (LFP) electrode. The preparation method of the LFP electrode preferably includes: mixing lithium iron phosphate active components, conductive carbon, a binder, and an organic solvent to obtain an electrode slurry; coating the electrode slurry onto an aluminum foil and drying it to obtain the LFP electrode. In this invention, the LFP electrode is preferably prepared using a wet electrode preparation method. In this invention, the conductive carbon is preferably Super C45; the binder is preferably polyvinylidene fluoride (PVDF); and the organic solvent is preferably N-methylpyrrolidone (NMP). In this invention, the mass ratio of the lithium iron phosphate active components, conductive carbon, and binder is preferably 7–9:0.5–2:0.5–1, more preferably 9:0.5:0.5, 8:1:1, or 7:2:1. In this invention, the solid content of the slurry is preferably 15–35%, more preferably 25%. The present invention does not have any particular limitation on the mixing method of the lithium iron phosphate active component, conductive carbon, binder and organic solvent, as long as the components are mixed evenly, magnetic stirring can be used.

[0053] In this invention, the encapsulation is preferably achieved by aluminum-plastic film heat sealing.

[0054] Figure 6 This is a schematic diagram illustrating the working principle of the lithium-ion battery assembled according to the present invention. During charging, the positive electrode LFP loses electrons, which can then reach the BP-based negative electrode (dry electrode plate) via the external circuit. Simultaneously, LFP loses Li... + Entering the electrolyte, Li + Further, under the influence of an electric field, lithium passes through the separator to reach the BP-based negative electrode. During discharge, electrons and Li... + The migration path is exactly the opposite; electrons transfer from the negative electrode to the positive electrode via the external circuit. + It passes through the membrane from the negative electrode to the positive electrode.

[0055] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0056] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; and the reagents and materials used are commercially available unless otherwise specified.

[0057] Example 1

[0058] (1) Weigh 0.7g of red phosphorus (RP) powder, 0.2g of carbon nanotubes (CNTs) and 0.1g of P3N5 powder and put them directly into a 35mL ball mill jar. Then add 20g of stainless steel grinding balls with a particle size of 5mm. Seal the ball mill jar in a glove box.

[0059] (2) Start the high-energy mill, set the speed to 875 cpm, and the working time to 24 h. Obtain the phosphorus-based doped modified electrode material in one step in an argon atmosphere, denoted as N-5%@BP / C.

[0060] Example 2

[0061] (1) Weigh 0.7g of RP powder, 0.2g of carbon nanotubes and 0.1g of Sb metal powder and put them directly into a 35mL ball milling jar. Then add 20g of stainless steel grinding beads with a particle size of 5mm. Seal the ball milling jar in a glove box.

[0062] (2) Start the high-energy mill, set the speed to 875 cpm, and the working time to 24 h. Obtain the phosphorus-based doped modified electrode material in one step in an argon atmosphere, denoted as Sb@BP / C.

[0063] Example 3

[0064] (1) Weigh 0.7g RP powder, 0.2g carbon nanotubes and 0.1g TiO2 powder and put them directly into a 35mL ball milling jar. Then add 20g stainless steel grinding beads with a particle size of 5mm. Seal the ball milling jar in a glove box.

[0065] (2) Start the high-energy mill, set the speed to 875 cpm, and the working time to 24 h. In an argon atmosphere, obtain the phosphorus-based doped modified electrode material in one step, denoted as Ti@BP / C.

[0066] Example 4

[0067] (1) Weigh 0.6g of RP powder, 0.2g of carbon nanotubes, 0.1g of Sb metal powder and 0.1g of P3N5 powder and put them directly into a 35mL ball milling jar. Then add 20g of stainless steel grinding balls with a particle size of 5mm. Seal the ball milling jar in a glove box.

[0068] (2) Start the high-energy mill, set the speed to 875 cpm, and the working time to 24 h. In an argon atmosphere, obtain the phosphorus-based doped modified electrode material in one step, denoted as Sb-N@BP / C.

[0069] Example 5

[0070] (1) Weigh 0.6g of RP powder, 0.2g of carbon nanotubes, 0.1g of metallic Ti powder and 0.1g of P3N5 powder and put them directly into a 35mL ball milling jar. Then add 20g of stainless steel grinding balls with a particle size of 5mm. Seal the ball milling jar in a glove box.

[0071] (2) Start the high-energy mill, set the speed to 875 cpm, and the working time to 24 h. In an argon atmosphere, obtain the phosphorus-based doped modified electrode material in one step, denoted as Ti-N@BP / C.

[0072] Example 6

[0073] The procedure was followed as in Example 1, except that the mass ratio of P3N5 was increased. Specifically, 0.65g of RP powder, 0.2g of carbon nanotubes, and 0.15g of P3N5 powder were subjected to high-energy ball milling. The resulting phosphorus-based doped modified electrode material was denoted as N-10%@BP / C.

[0074] Comparative Example 1

[0075] The preparation method is basically the same as that in Example 1, except that 0.1g of P3N5 powder is omitted, and 0.7g of RP and 0.3g of carbon nanotubes are subjected to high-energy ball milling to obtain BP / C anode material.

[0076] Comparative Example 2

[0077] The preparation method is basically the same as in Example 1, except that carbon nanotubes and P3N5 powder are omitted, and only red phosphorus (RP) powder is used for high-energy ball milling to obtain BP.

[0078] Application Example 1

[0079] (1) Weigh 0.8g of Ti-N@BP / C solid powder prepared in Example 5, 0.1g of conductive carbon Super C45 and 0.1g of polytetrafluoroethylene (PTFE) solid powder and place them in a mortar. Then add 0.2g of isopropanol and stir magnetically for 10min. During the stirring process, set the temperature to 50℃ and wait for the isopropanol to evaporate completely. Transfer the uniformly mixed material to the mortar and grind manually for 10min to obtain a uniformly mixed electrode mixture that is similar to putty.

[0080] (2) The above electrode mixture was repeatedly rolled using a roller press, with rolling heights set sequentially to 20 mm, 15 mm, 10 mm, 5 mm, and 1 mm. Finally, the resulting dry electrode was placed on the surface of the copper foil current collector and rolled using a minimum height of 50 μm. The surface loading of the electrode mixture was 1.1 g·cm³. -2 ;

[0081] (3) The copper foil current collector coated with the electrode mixture is transferred to a vacuum drying oven and dried at 60°C for 12 hours to obtain a dry electrode sheet.

[0082] Test case

[0083] Following the preparation method of Application Example 1, the electrode materials of Examples 1-6 and Comparative Examples 1-2 were all prepared into dry electrode sheets, and then assembled into button cells and lithium-ion full cells for electrochemical performance testing.

[0084] Using lithium metal sheets as the counter and reference electrodes, a polypropylene microporous membrane (Celgard 2400) as the separator, and a 1.0 mol / L LiPF6 solution (a mixture of ethylene carbonate EC, dimethyl carbonate DMC, diethyl carbonate DEC, and fluoroethylene carbonate FEC in a volume ratio of 1:1:1:0.1) as the electrolyte, CR 2025 coin cells were assembled in a glove box. Dry-processed electrode sheets, separators, lithium metal sheets, gaskets, and spring contacts were stacked sequentially into a layered structure, then the electrolyte was added, and the cells were sealed using a hydraulic press to obtain the CR 2025 coin cell. The assembled CR 2025 coin cells were then transferred to a Xinwei charge-discharge tester for constant current charge-discharge cycle testing, with the current density set to 0.2 A·g. -1 (Based on the quality of the active material), the cutoff voltage is set to 0.01–3.0V.

[0085] LFP electrodes were prepared using a traditional wet electrode method: Lithium iron phosphate (LFP), conductive carbon (Super C45), and binder (PVDF) were mixed at a mass ratio of LFP:Super C45:PVDF of 7:2:1. NMP was added at a solid content of 25%. The mixture was then magnetically stirred at 300 rpm for 8 hours to obtain an electrode slurry. This slurry was coated onto aluminum foil and transferred to a forced-air drying oven at 80°C for 8 hours, followed by a vacuum drying oven at 100°C for 10 hours. The dried electrode was then cut into electrode sheets with a size of 35 × 40 mm. 2 The square sheet was used as the positive electrode. Using the same electrolyte and separator as the CR 2025 coin cell assembled above, the dry-process electrode sheets corresponding to Examples 1-6 and Comparative Examples 1-2 were used as the negative electrode. Aluminum tabs were welded to the positive electrode, and nickel tabs were welded to the negative electrode. In a glove box, the lithium sheet / separator / negative electrode / separator / positive electrode were stacked and fixed in that order, placed in an aluminum-plastic film, and then the electrolyte was added. After vacuum sealing, a lithium-ion full battery was obtained. The assembled lithium-ion full battery was transferred to a Newway charge-discharge tester for constant current charge-discharge cycle testing, with the current density set to 1 A·g. -1 (Based on the mass of the positive and negative electrode active materials), the cutoff voltage is set to 1–4.2V.

[0086] Characterization and test results

[0087] Figure 1 SEM images of the electrode materials prepared by RP, Examples 1-5, and Comparative Examples 1-2. Except for the red phosphorus particles, which have a relatively large particle size (approximately 20 μm), the other samples treated with high-energy ball milling showed a significant reduction in size, with an average size of less than 5 μm, and the particles exhibited similar agglomeration morphologies. This is because during the high-energy ball milling process, the RP is continuously sheared, rubbed, and collided, resulting in the crushing of large particles and the agglomeration of small particles.

[0088] Figure 2 The images show the XRD patterns of the electrode materials prepared in Examples 1-5 and Comparative Examples 1-2. It can be seen that amorphous red phosphorus, after high-energy ball milling, is transformed into polycrystalline black phosphorus, and the external carbon layer weakens the black phosphorus crystal signal. Meanwhile, the Sb and Ti doped within the carbon layer retain their crystal structure, while the inorganic dopant P3N5 crystal is transformed into an amorphous structure after high-energy ball milling.

[0089] Figure 3 Raman spectra of the electrode materials prepared in Examples 1-5 and Comparative Examples 1-2. All samples that underwent high-energy ball milling at 1300 cm⁻¹... -1 and 1600cm -1 Characteristic peaks for carbon materials, D and G, appear at both positions. The dopant component, due to its relatively low content, does not exhibit a significant signal.

[0090] Figure 4 The charge-discharge curves of CR 2025 coin cells assembled with dry-process electrode sheets corresponding to Examples 1-6 and Comparative Examples 1-2 are shown. Under the same test conditions, Examples 1-6 compared and analyzed the effects of metal doping and non-metals on phosphorus-based materials. The results showed that the combination of metal and non-metal, i.e., the Ti-N@BP / C co-doped sample, exhibited the highest reversible capacity and the largest capacity retention. Figure 4 (a) indicates that without carbon coating and doping modification, the phosphorus-based material has a reversible capacity of only 18.5 mAh / g after 20 cycles, which is far lower than its theoretical specific capacity. This is because the volume expansion of the phosphorus-based material causes irreversible loss of active material, resulting in loss of current-current contact and inability to continue processing. Figure 4(b) shows that when only carbon-coated BP / C is applied to a phosphorus-based material, the reversible discharge capacity reaches 1470 mAh / g in the first two cycles. However, after 20 cycles, the discharge capacity rapidly decays to 695.4 mAh / g, with a capacity retention of less than 50%. This rapid capacity decay is mainly due to the unstable cycling structure. As the number of cycles increases, there is an uneven distribution of electrons and ions inside the BP / C. The electron and ion concentration is high on the outside, while only a small number of electrons and ions can be conducted into the phosphorus-based material. The accompanying uneven strain causes cracking and pulverization of the BP / C. The newly formed crack sites further form new SEI layers, resulting in a large loss of lithium ions, hence the rapid decay of the reversible capacity. Figure 4 Tables (c) to (h) compare the modification of phosphorus-based materials by non-metallic N doping, metallic Sb, Ti doping, and metal-non-metal co-doping. The specific reversible specific capacity and capacity retention data are shown in Table 1. The comparison shows that the cycle life of the composite electrode after doping modification is significantly improved. After 20 cycles, the capacity retention is higher than 80%. In particular, the Ti-N@BP / C co-doped sample has a discharge capacity of 1146.8 mAh / g in the first cycle and a reversible capacity of 994.3 mAh / g after 20 cycles at a current density of 0.2 A / g, with the capacity retention increasing to 86.7%. The improved cycle life is due to the following reasons: First, the doping components Ti and N alter the band structure of the semiconductor phosphorus-based material, reducing its band gap and exhibiting metal-like high conductivity. Second, Ti and N components have a strong adsorption force for lithium ions, which can pre-store lithium ions before lithium intercalation in the phosphorus-based material, uniformly dispersing electrons and lithium ions inside the electrode, avoiding uneven deposition of lithium ions inside the electrode, and stabilizing its electrode structure. Third, the doped components can chemically bond with the phosphorus-based material at the interface, stabilizing the BP interface structure and preventing irreversible structural damage caused by lithium ion diffusion.

[0091] Table 1 Reversible capacity and retention of phosphorus-doped modified electrode materials

[0092]

[0093] Figure 5 To assess the electrochemical performance of the lithium-ion full cell assembled with a Ti-N@BP / C anode and a lithium iron phosphate cathode in Example 5, the cutoff voltage range of the full cell was optimized. Figure 5 (a)), the mass ratio of positive to negative electrode active materials ( Figure 5 (b) In this invention, a lithium-ion full battery is assembled within a voltage range of 1–4.2V, with a mass ratio of positive to negative electrode active materials of 1:2. The charge-discharge curve of the lithium-ion full battery is shown below. Figure 5 As shown in (c), the lithium storage platform at the 3.3V position corresponds to the lithium iron phosphate cathode. Figure 5(d) and (e) correspond to the rate performance and Lagrangian of the lithium-ion full battery, respectively, showing a performance of 267.45 Wh / kg. -1 and 2.5kWkg -1 The high energy density and high power density achieved the goal of fabricating this dual-high device. Finally, this invention also... Figure 5 (f) gives the cycle life of the full cell under a high current of 1A / g. After 2400 charge-discharge cycles, the capacity has almost no decay, which is far superior to the performance of most lithium-ion batteries reported to date.

[0094] This invention employs a metal-nonmetal co-doping method for phosphorus-based materials, which significantly improves their cycle life. This is because the Ti-N@BP / C composite anode material, through its carbon coating and the doping elements Ti / N, jointly suppresses the volume expansion and poor conductivity issues of phosphorus-based materials after lithium intercalation. Furthermore, the conductivity of the carbon and Ti / N components is much higher than that of semiconductor phosphorus, significantly improving the rate performance and cycle performance of the phosphorus-based composite material. This provides a new approach and solution for the practical application and commercialization of phosphorus-based anode materials.

[0095] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a phosphorus-based doped modified electrode material, comprising the following steps: Phosphorus-based materials, carbon materials, and doped materials are mixed and subjected to high-energy ball milling in a protective atmosphere to obtain phosphorus-based doped modified electrode materials; the high-energy ball milling speed is 100~1000 cpm. The doping materials are TiO2 and P3N5.

2. The preparation method according to claim 1, characterized in that, The phosphorus-based material includes one or more of white phosphorus, red phosphorus, and black phosphorus.

3. The preparation method according to claim 1, characterized in that, The carbon material includes one or more of flake graphite, expanded graphite, graphene, and carbon nanotubes.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the phosphorus-based material, carbon material and doped material is 50~90:10~20:5~20.

5. The preparation method according to claim 1, characterized in that, The high-energy ball milling time is 12~240h.

6. The phosphorus-based doped modified electrode material prepared by the preparation method according to any one of claims 1 to 5.

7. A dry-process electrode sheet, characterized in that, The phosphorus-based doped modified electrode material as described in claim 6 is used as the active component.

8. A method for preparing a dry electrode sheet, comprising the following steps: An electrode mixture is obtained by mixing an active component, conductive carbon, a binder, and a dispersant; the active component is the phosphorus-based doped modified electrode material as described in claim 6. The electrode mixture is repeatedly rolled to the target thickness, and then the resulting dry electrode is pressed onto the current collector and dried to obtain a dry electrode sheet.

9. The application of the phosphorus-based doped modified electrode material of claim 6, the dry electrode sheet of claim 7, or the dry electrode sheet prepared by the preparation method of claim 8 in lithium-ion batteries or lithium-ion capacitors.

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