Carbon-supported black phosphorus-red phosphorus heterostructure materials, their preparation methods, negative electrodes, and rechargeable batteries

Abstract

This application relates to a carbon-supported black phosphorus / red phosphorus heterostructure material, wherein black phosphorus / red phosphorus grains grow alternately along the longitudinal axis of the carbon material, and each black phosphorus / red phosphorus grain includes at least two black phosphorus / red phosphorus heterostructures; the black phosphorus / red phosphorus grains have a core-shell structure, wherein crystalline elemental black phosphorus forms the core and amorphous elemental red phosphorus forms the shell. This application also provides a method for preparing the carbon-supported black phosphorus / red phosphorus heterostructure material. This application further provides a negative electrode made of the carbon-supported black phosphorus / red phosphorus heterostructure material and a rechargeable battery including the negative electrode. The black phosphorus / red phosphorus grains described herein include a large number of black phosphorus / red phosphorus heterostructures, which form numerous heterostructure interfaces, facilitating metal ion migration and charge rearrangement, and exhibiting excellent stability. Therefore, when used as a negative electrode for lithium, sodium, and potassium-ion batteries, they possess excellent rate performance and cycle performance.

Description

Technical Field

[0001] This invention belongs to the field of batteries, specifically relating to a carbon-supported black phosphorus-red phosphorus heterostructure material, a method for preparing the carbon-supported black phosphorus-red phosphorus heterostructure material, a negative electrode made of the carbon-supported black phosphorus-red phosphorus heterostructure material, and a rechargeable battery including a negative electrode made of the carbon-supported black phosphorus-red phosphorus heterostructure material. Background Technology

[0002] Sodium-ion and potassium-ion batteries are promising candidates for sustainable and grid-scale energy storage. [1] Sodium and potassium are abundant in the Earth's crust and could address the unsustainability of lithium-ion batteries, attracting widespread interest from academia and industry. [2] In particular, among potassium-ion battery anode materials, elemental phosphorus, especially red phosphorus (RP), has advantages such as low cost and high theoretical specific capacity (2596 mAh g⁻¹ when the product is K₃P). -1 The redox potential is also quite ideal (0.6 V vs. K / K). + Potassium phosphorus has advantages such as high conductivity, making it an ideal candidate material. However, the large radius of potassium ions and slow reaction kinetics typically lead to poor battery rate capability. Furthermore, red phosphorus has poor conductivity (10⁻⁶ ppm). -14 S cm -1 This hinders the transfer of electrons within it. [2,3] This results in potassium ions being adsorbed only on the surface of red phosphorus, leading to dendrite formation under high current density. [4-8] .

[0003] Therefore, the search for deep potassium-based products (such as K3P) remains a significant challenge for the entire field, especially under high-rate conditions. To address these challenges, existing literature has investigated the optimization of phosphorus size / morphology and its composite with carbon materials. [9,10] This improves electron and ion transfer to some extent. However, the root cause of the phosphorus problem remains unresolved: the slow diffusion and reaction kinetics within phosphorus. Therefore, achieving deep, reversible potassium ion storage based on elemental phosphorus anodes is crucial, but remains challenging to date. [11-13] .

[0004] For other rechargeable batteries such as lithium batteries and sodium batteries, there is still a need to continuously develop anode materials with better performance.

[0005] References:

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[15] X. Jiang, H. Liu, J. Song, C. Yin, H. Xu, J. Mater. Chem. A 2016, 4 , 16205.

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[16] H. Sun, P. Liang, G. Zhu, WH Hung, YY Li, HCTai, CLHuang, J. Li, Y. Meng, M. Angell, CA Wang, H. Dai, Proc. Natl. Acad. Sci. USA 2020, 117 , 27847. Summary of the Invention

[0022] Studies have shown that rational heterostructure processing is an effective strategy to improve the slow diffusion and reaction kinetics of potassium ions in elemental phosphorus. The inventors designed and prepared alternating black phosphorus / red phosphorus heterostructures and anchored them, for example, on multi-walled carbon nanotubes (BRPH@MWCNT) or on carbon fibers (BP / RP@CF). The abundant heterostructure interfaces significantly promoted the adsorption, implantation, and migration of potassium ions at 0.05 A g. -1 It provides 923 mAh g -1 High specific capacity, at 1 Ag -1 It provides 335 mAh g -1 Its excellent rate performance at 0.8 A g -1 The phosphorus heterostructure induced a KF-rich interfacial layer, exhibiting excellent cycling stability after 300 cycles and effectively improving electrochemical reversibility. In-situ X-ray diffraction and time-of-flight secondary ion mass spectrometry confirmed the formation of K3P, representing a breakthrough in the deep potassiumization of elemental phosphorus anodes. The inventors' findings have resolved a long-standing bottleneck in elemental phosphorus anodes for potassium-ion batteries and opened new avenues for activating other slow / irreversible battery chemical reactions.

[0023] To achieve this objective, the present invention employs the following technical solution.

[0024] In a first aspect, this application provides a carbon-supported black phosphorus / red phosphorus heterostructure material, wherein black phosphorus / red phosphorus grains grow alternately along the longitudinal axis of the carbon material, and each black phosphorus / red phosphorus grain includes at least two black phosphorus / red phosphorus heterostructures. In this embodiment, the black phosphorus / red phosphorus grain has a core-shell structure, wherein crystalline elemental black phosphorus forms the core and amorphous elemental red phosphorus forms the shell.

[0025] In one embodiment of the first aspect, the carbon material is carbon nanotubes or carbon fibers.

[0026] In a second aspect, this application provides a method for preparing a carbon-supported black phosphorus-red phosphorus heterostructure material, the method comprising subjecting red phosphorus, a phosphorus chain attacking agent and a carbon material to a solvothermal reaction to obtain the carbon-supported black phosphorus-red phosphorus heterostructure material.

[0027] In one embodiment of the second aspect, the method includes the following steps: S1: subjecting the red phosphorus, the phosphorus chain attacking agent, and the carbon material to a solvothermal reaction to obtain the carbon-supported black phosphorus-red phosphorus heterostructure material.

[0028] In one embodiment of the second aspect, the method includes the following steps: S11, pretreating red phosphorus to remove surface oxide residues of red phosphorus to obtain loose red phosphorus; S13: subjecting the loose red phosphorus, the phosphorus chain attacking agent, and the carbon material to a solvothermal reaction to obtain the carbon-supported black phosphorus-red phosphorus heterostructure material.

[0029] In one embodiment of the second aspect, the carbon material is a carbon nanotube or a carbon fiber.

[0030] In one embodiment of the second aspect, the phosphorus chain attacking agent is ethylenediamine or a mixture of ethylenediamine and N,N-dimethylformamide.

[0031] In one embodiment of the second aspect, the mass ratio of red phosphorus, phosphorus chain attack agent and carbon material is 7.5: 216-108: 1, based on weight.

[0032] In one embodiment of the second aspect, the reaction conditions for the solvothermal reaction are: a closed reaction vessel, a reaction temperature of 120-180°C, and a reaction time of 12-48 hours.

[0033] In a third aspect, this application provides the use of carbon-supported black phosphorus-red phosphorus heterostructure materials as described in the first aspect as battery anode materials.

[0034] In a fourth aspect, this application provides a negative electrode made of a carbon-supported black phosphorus-red phosphorus heterostructure material as described in the first aspect.

[0035] In a fifth aspect, this application provides a rechargeable battery comprising a negative electrode as described in the fourth aspect. In this embodiment, the rechargeable battery may be a lithium-ion battery, a sodium-ion battery, or a potassium-ion battery.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] This invention provides a carbon-supported black phosphorus-red phosphorus heterostructure material suitable for use as a negative electrode in rechargeable batteries via a solvent method. Because the black phosphorus / red phosphorus grains comprise a large number of black phosphorus-red phosphorus heterostructures, these heterojunctions form numerous heterostructure interfaces, facilitating metal ion migration and charge rearrangement. This results in a high specific capacity for rechargeable batteries when used as a negative electrode. Furthermore, these heterojunctions exhibit excellent stability and rate performance. Attached Figure Description

[0038] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0039] Figure 1 The images are SEM images of RP and RP@MWCNT after preprocessing, where the scale bar of a is 1 μm and the scale bar of b is 100 nm.

[0040] Figure 2 The adsorption / desorption isotherms for BRPH@MWCNT and RP@MWCNT are given. Based on the BET method, the specific surface areas of BRPH@MWCNT and RP@MWCNT are 22.73 and 62.00 m², respectively. 2 g -1 .

[0041] Figure 3 Characterization of the black / red phosphorus heterostructure, including: a) Schematic diagram of the structure and charge transfer mechanism of BRPH@MWCNT. BRPH exhibits a "wheat"-like structure, uniformly distributed on the MWCNT substrate. The heterostructure promotes potassium ion migration and charge rearrangement, enhancing potassium ion storage performance. b) SEM image of BRPH@MWCNT. Scale bar, 200 nm. c) Elemental mapping of BRPH@MWCNT using energy-dispersive X-ray spectroscopy (EDS). Scale bar, 50 nm. d) Detection of BRPH formation using high-resolution transmission electron microscopy. Scale bar, 5 nm. The inset shows the Fast Fourier Transform (FFT) modes of RP and BP. e) XRD patterns of BRPH@MWCNT and RP@MWCNT. f) Raman spectra of MWCNT, RP, and BRPH@MWCNT.

[0042] Figure 4 The electrochemical performance of BRPH@MWCNT is shown, with CV curves for α, BRPH@MWCNT (BP / RP ratio of 0.9). Scan rate: 0.1 mV s. -1 b, current density is 0.05 A g −1c. Constant current charge-discharge curves of RP@MWCNT and BRPH@MWCNT at different current densities. d. Comparison of rate performance of RP@MWCNT and BRPH@MWCNT at different current densities. −1 Cyclic performance of RP@MWCNT and BRPH@MWCNT at current densities. Unless otherwise specified, the BP / RP ratio is 0.9 for all BRPH@MWCNT samples.

[0043] Figure 5 The constant current charge-discharge curves of the K metal / MWCNT half-cell are shown, where the electrolyte is an EC / DMC solution of 4 M KFSI and 1 MKTFSI (volume ratio 1:1).

[0044] Figure 6 0.8 A g −1 Cyclic performance of RP@MWCNT and BRPH@MWCNT at current densities.

[0045] Figure 7 Potassium kinetic analysis, where a and b are EIS analyses based on the 2.5–0.01 V potassium kinetics of RP@MWCNT and BRPH@MWCNT. Tests were performed at 0.1 A g. -1 The next cycle is performed after 20 cycles. An insert shows the equivalent circuit of the fitting, where Rs and Rct represent the solution resistance and charge transfer resistance, respectively. CPE is the phase constant element, and Zw is the Warburg impedance. c, Comparison of potassium ion diffusion coefficients (DK+) of RP@MWCNT and BRPH@MWCNT obtained by GITT measurement. d and e are the CV curves of RP@MWCNT and BRPH@MWCNT at different scan rates, respectively. f, Diffusion capacity contribution of BRPH@MWCNT and RP@MWCNT.

[0046] Figure 8 Intermittent galvanostatic titration (GITT) curves for the negative electrodes of BRPH@MWCNT and RP@MWCNT.

[0047] Figure 9 The CV performance of RP@MWCNT and BRPH@MWCNT at different scan rates is shown, where a and b are displayed from 0.1 to 1.2 mV s. −1 CV curves of RP@MWCNT at different scan rates (two parallel sets), c, d are shown in the range of 0.1 to 1.2 mV s. −1 CV curves of BRPH@MWCNT at different scan rates (two parallel sets).

[0048] Figure 10This describes a rapid, deep potassic reaction based on a BP / RP heterostructure. a) In-situ XRD pattern of BRPH@MWCNTs during the first discharge / charge cycle. b) TOF-SIMS 3D distribution map of potassic products in a fully discharged BRPH@MWCNT sample. Analysis area: 100 × 100 μm. 2 .

[0049] Figure 11 The XRD patterns of BRPH@MWCNT after potassium insertion and depotassium removal are shown.

[0050] Figure 12 This is an HRTEM image of BRPH@MWCNT after complete potassium intercalation.

[0051] Figure 13 Four fragment ion peaks (K4P) measured by TOF-SIMS after potassium intercalation in BRPH@MWCNT + K4P3 + K3P + and KP + The distribution of ).

[0052] Figure 14 XPS F1s spectra of BRPH@MWCNT and RP@MWCNT, both samples at 100 mA g. −1 Cycle 20 times at a current density.

[0053] Figure 15 Displaying the BRPH@MWCNT / Prussian Blue full cell. a, Schematic diagram of the BRPH@MWCNT / Prussian Blue full cell. b, K-metal / BRPH@MWCNT half cell, K-metal / Prussian Blue half cell, and BRPH@MWCNT / Prussian Blue full cell at 100 mA g. −1 Charge-discharge curves at current density. c. Rate performance of the BRPH@MWCNT / Prussian Blue full cell (N / P ratio of 1.4). d. Rate performance of the BRPH@MWCNT / Prussian Blue full cell at 300 mA g. −1 Cyclic performance at current density.

[0054] Figure 16 The XRD pattern of the Prussian blue cathode.

[0055] Figure 17 Rate performance of K metal / Prussian blue half-cell at different current densities.

[0056] Figure 18 The rate performance of the BRPH@MWCNT / Prussian Blue full cell is given, with an N / P ratio of 1.4:1.

[0057] Figure 19 The cycle performance and corresponding charge-discharge curves of the RP@MWCNT / Prussian Blue full cell were obtained at a current density of 200 mA g. -1 The N / P ratio is 1.3:1. This battery was first tested at 20 mA g... -1 It is cycled 3 times at a current density to form a stable solid electrolyte layer (SEI).

[0058] Figure 20 The cycle performance of the BRPH@MWCNT / Prussian Blue full cell is evaluated, with an N / P ratio of 1.1. The cell was first tested at 20 mA g... -1 It is cycled 3 times at a current density to form a stable solid electrolyte layer (SEI).

[0059] Figure 21 Cycle performance of BRPH@MWCNT (160°C-24h) for lithium-ion battery anodes.

[0060] Figure 22 The image shows the morphology of BP / RP@MWCNT synthesized using ethylenediamine:DMF = 1:1 v%.

[0061] Figure 23 The potassium-ion battery cycle performance of BP / RP@MWCNT synthesized using ethylenediamine:DMF=1:1 v% is evaluated.

[0062] Figure 24 SEM image of carbon fibers (BP / RP@CF) supported on a red phosphorus-black phosphorus heterostructure.

[0063] Figure 25 Raman spectra of carbon fibers (BP / RP@CF) supported on red phosphorus-black phosphorus heterostructure.

[0064] Figure 26 Charge-discharge curves of a sodium-ion battery with BP / RP@CF negative electrode.

[0065] Figure 27 The cycle performance of sodium-ion batteries with BP / RP@CF anode.

[0066] Figure 28 Rate performance of potassium-ion batteries with BP / RP@CF anode. Detailed Implementation

[0067] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0068] Example 1

[0069] This embodiment relates to the synthesis of MWNT-supported black phosphorus-red phosphorus heterostructures and the performance testing of potassium batteries, with ethylenediamine as the phosphorus chain attacking agent.

[0070] The experimental steps of this embodiment are as follows.

[0071] Synthesis of BRPH@MWCNT and RP@MWCNT

[0072] BRPH@MWCNT was prepared via a solvothermal method. Multi-walled carbon nanotubes (MWCNTs) were used as a substrate, commercial red phosphorus (97%, Titan) as a precursor, and ethylenediamine (AR, Sinopharm) solution as a phosphorus chain attacking agent and structural remodeling agent. Typically, red phosphorus was hydrothermally pretreated in a stainless steel autoclave at 200°C for 12 hours to remove surface oxide residues and produce loose RP. 450 mg of pretreated RP was added to 30 mL of ethylenediamine solution and stirred at 500 rpm for 30 min. Then, 60 mg of MWCNT was added and gently stirred for 30 min. The resulting suspension was solvothermally treated at 160°C for 24 h, resulting in RP crystallization / phase transformation to BP under high pressure. After cooling to room temperature, the black precipitate at the bottom was collected and washed several times with deionized water by centrifugation until the washings were nearly neutral. The precipitate was then freeze-dried to obtain the BRPH@MWCNT product.

[0073] RP@MWCNT was synthesized using a similar method. To avoid BP formation, the RP-ethylenediamine solution was acid-treated to precipitate nano-RP on MWCNTs. Simply put, 450 mg of pretreated RP was dissolved in 30 mL of ethylenediamine solution with stirring. 60 mg of MWCNT was dispersed in 100 mL of dilute nitric acid (0.05 M, Sinopharm) and 5 mL of ethanol (AR, Sinopharm). After sonicating the MWCNT suspension for 10 min with continuous stirring, the suspension was added dropwise to the RP-ethylenediamine solution. The RP@MWCNT product was then collected and washed using the same procedure as for BRPH@MWCNT.

[0074] Preparation of electrodes and electrolytes

[0075] Ketjen Black (KJ, Shenzhen Kejing) and sodium alginate (SA, AR grade, Aldrich) were used as the conductive agent and binder, respectively. Copper foil and aluminum foil were used as the current collectors for the negative and positive electrodes, respectively. Typically, BRPH@MWCNT (70 wt%), KJ (15 wt%), and SA (15 wt%) were ground using agate slurry and dispersed in water to form a slurry. The slurry was cast onto pre-cleaned copper foil using a scraper and dried at room temperature for 5 hours. The resulting electrode was cut into circular foils with a diameter of 12 mm and a mass loading of ~1 mg / cm². 2 Then, Prussian blue cathode material was synthesized. [14,15] The mass loading of the positive electrode is 3.7 ~ 4.8 mg cm⁻¹. -2 For electrolyte preparation, 4 M potassium bis(fluorosulfonyl)imide (KFSI, battery grade, DodoChem) and 1 M potassium bis(trifluorosulfonyl)imide (KTFSI, battery grade, DodoChem) were used as electrolytes, prepared by mixing ethyl carbonate (EC, anhydrous, Titan) and dimethyl carbonate (DMC, Adamas, 99%) solutions in a 1:1 volume ratio. The salts of KFSI and KTFSI were dried in a vacuum oven at 120°C before use, and the electrolyte was dried using molecular sieves.

[0076] Electrochemical testing

[0077] Electrochemical measurements were performed using CR2032 coin cells. All cells were assembled in an argon glove box with O2 < 1 ppm and H2O < 0.5 ppm. K metal (Sigma Aldrich) was first washed with anhydrous DMC, then the oxide layer on the surface was scraped off with a clean blade, and then pressed into a thin foil. A GF / D membrane (Whatman) was used as the separator. All cells were aged for 6 hours and tested on a Neware battery testing system. Cells were assembled in coin cells or aluminum-layered pouches in a glove box, following typical procedures from previous work.

[16] Prior to assembling and testing the full cell, the BRPH@MWCNT negative electrode was pre-potassium-treated with K metal and discharged to ~0.1 V to form a stable SEI. For the assembly of the pouch cell, Prussian blue positive electrode foil and BRPH@MWCNT negative electrode foil were bonded to the pouch layer with carbon adhesive (Ted Pella). Two nickel sheets and a GF / A separator (Whatman) served as the current collector and separator, respectively. Each pouch cell required approximately 400 µL of electrolyte. After heat sealing, this pouch cell was used to power a mobile phone. Constant current charge-discharge was performed on the Prussian blue-paired full cell within a voltage window of 1–4.12 V. The current density and capacity were calculated based on the total mass of active material on the positive and negative electrodes. The N / P ratio was based on a BRPH@MWCNT negative electrode capacity of 800 mAh g. −1 The capacity of the Prussian blue cathode is 120 mAh g. −1 Calculated. Based on total active material, the 1C of the full cell is set to 120 mA g. −1 EIS analysis was performed on a CHI660E electrochemical workstation, with a frequency range of 0.01 Hz to 100 kHz.

[0078] The experimental results and analysis of this embodiment are as follows.

[0079] The inventors synthesized BRPH@MWCNT via a solvothermal method. Simply put, ethylenediamine, acting as a phosphorus chain attacker and structure rebuilder, induces the phase transformation of red phosphorus (RP) to black phosphorus (BP) under hydrothermal conditions. Each BP / RP grain consists of numerous BP / RP heterojunctions, forming a large number of heterostructure interfaces that facilitate potassium ion migration and charge rearrangement. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) confirmed the alternating growth of BP / RP grains along the MWCNT axis. High-resolution transmission electron microscopy (HRTEM) confirmed the formation of abundant interfaces between BP and RP, resulting in a large number of heterojunctions. Figure 3 Abundant heterojunctions are crucial for promoting potassium ion migration, but previous BP / RP structure designs lacked proper control over the morphology and configuration of the heterostructure. As a comparative sample, the inventors synthesized RP@MWCNT using the same preparation process as the heterojunction material, but without phase transition treatment. During the preparation of RP@MWCNT and BRPH@MWCNT, the mass ratio of phosphorus (P) to MWCNT reactants, solvent, and washing conditions was strictly controlled. Therefore, the phosphorus content of RP@MWCNT and BRPH@MWCNT could be controlled, ensuring the validity of the comparative experiments.

[0080] X-ray diffraction (XRD) confirmed the formation of the BP / RP heterostructure. Broad peaks at 15.2°, 32.4°, and 55.8° indicate that RP is an amorphous structure. For the BP / RP heterostructure, new peaks at 16.4° (5.2 Å), 25.9° (3.4 Å), and 33.0° (2.7 Å) correspond to the (002), (012), and (004) planes of BP (JCPDS #09-0020). Raman spectroscopy confirmed the formation of the BP (A g 1 B 2g and A g 2 The peaks are located at 362.8, 444.7, and 470.0 cm. -1 The peaks for RP (B1, A1, and E1) are located at 350.1, 395.0, and 450.2 cm⁻¹, respectively. -1 )coexist.

[0081] The potassium ion storage performance of BRPH@MWCNT was investigated using 4 M potassium difluorosulfonylimide (KFSI) and 1 M potassium difluorosulfonylimide (KTFSI) as electrolytes in a 1:1 volume ratio of ethylene carbonate (EC) and dimethyl carbonate (DMC). Cyclic voltammetry (CV) revealed a prominent broad peak at ~0.76 V on the initial cathode scan, corresponding to irreversible electrolyte decomposition and the formation of a solid electrolyte interphase (SEI). A sharp reduction peak at 0.01 V (shifting to 0.23 V in subsequent cycles) is associated with the formation of KxP alloys. Oxidation peaks at 0.78 V and 2.36 V, respectively, belong to the stepwise dealloying process of KxP. Good overlap curves in subsequent cycles indicate good electrochemical reversibility during cycling. Figure 4 a). K-metal / BRPH@MWCNT half-cell at 0.05 A g −1 The specific capacity is as high as 923 mAh g. −1 The specific capacity of RP@MWCNT is only 600 mAh g. −1 ( Figure 4 b). Furthermore, the overpotential of BRPH@MWCNT (~0.25 V) is significantly lower than that of RP@MWCNT (~0.5 V), indicating that the BP / RP heterostructure facilitates charge transfer. Reference Figure 5 The inventors also verified in BRPH@MWCNT that the capacity contributed by the MWCNT substrate is very small.

[0082] Furthermore, the inventors investigated the cycling performance of BRPH@MWCNT and RP@MWCNT at different current densities. At 0.1 A g −1At low current densities, BRPH@MWCNT achieves 428.8 mAh g⁻¹ after 100 cycles. −1 The reversible specific capacity is higher, while RP@MWCNT only has 184.0 mAh g after 100 cycles. −1 ( Figure 4 d). The RP@MWCNT exhibits rapid capacity decay, retaining only 19.6% of its original capacity after 100 cycles. (Reference) Figure 6 At a higher current density of 0.8 A g −1 Upon testing, BRPH@MWCNT first exhibited an increase in capacity, which stemmed from the continuous activation of the active material within BRPH@MWCNT, maintaining 83.3% of its original capacity after 300 cycles. This indicates that the BP / RP heterostructure significantly improves the reversibility of the KP alloying / dealloying process.

[0083] Furthermore, the change in charge transfer resistance (Rct) during continuous potassiumization was investigated using electrochemical impedance spectroscopy (EIS). RP@MWCNT exhibited large Rct values, such as 1,410 Ω (2.5 V) and 7,458 Ω (0.01 V). Figure 7 a) This indicates a poor potassium ion transfer capacity during potash formation. In contrast, the Rct values ​​for BRPH@MWCNT are much lower, for example, 600 Ω (2.5 V) and 981 Ω (0.01 V). Figure 7 b) This indicates that potassium ions have a highly efficient transfer capability. Furthermore, referring to... Figure 7 c and Figure 8 The inventors demonstrated, through intermittent potentiostatic titration (GITT) on a potassium intercalation platform (0.53 ~ 0.27 V), that the potassium ion diffusion coefficient (D) of BRPH@MWCNT was [missing value]. K+ The value was significantly higher than that of RP@MWCNT, indicating that the heterostructure facilitated potassium ion diffusion. Kinetic studies showed that at 0.1 and 0.2 mV s... -1 At low scan rates, both BRPH@MWCNT and RP@MWCNT exhibited high diffusion contributions (above 70%). At higher scan rates (e.g., 1.2 mV s⁻¹), the diffusion contribution was significantly higher. -1 The BRPH@MWCNT anode maintained a diffusion contribution of over 60%. Figure 7 f). In stark contrast, the diffusion contribution of RP@MWCNT rapidly declined to below 32% ( Figure 7 d−f and Figure 9 This confirms the effective regulation of potassium ion migration by the abundant heterojunction between BP and RP.

[0084] The inventors further used in-situ XRD to detect the evolution of potassium-containing / potassium-containing products during battery cycling. Figure 10 a). During the initial discharge, within the voltage range of 2.4 ~ 1.0 V, the XRD pattern showed a diffraction peak at 29.7°, corresponding to the (130) plane of K4P3 (JCPDS No. 79−0033). Further discharge to 0.20 V resulted in an enhanced K4P3 peak and the appearance of a new Bragg peak at 18.2°, corresponding to the (100) plane of K3P (JCPDS No. 74−0128). Finally, at approximately 0.01 V, the intensity of the K4P3 peak decreased, and the K3P peak became dominant. Figure 10 a) indicates that the final potassation product of BRPH@MWCNT is K3P. During the depotassation process, the XRD peak intensities of K3P and K4P3 decrease, indicating that the potassation / depotassation process has good reversibility. The formation of K3P was further verified by in-situ XRD and HRTEM. Figure 11 and Figure 12 These results indicate that the BP / RP heterostructure efficiently modulates the adsorption and diffusion kinetics of potassium ions, thereby alleviating the slow and capacitive potassium ion storage at the elemental phosphorus anode, thus enabling a deep potassization process with K3P as the final potassization product.

[0085] Time-of-flight secondary ion mass spectrometry (TOF-SIMS) further confirmed the formation of K3P. The depth distribution map of KxP secondary ion fragments showed that the order of ion intensity was K4P. + K4P3 + K3P + KP + ( Figure 13 This indicates that K3P (fragment signals are K4P) is the correct fragment. + and K3P + K2P5 is one of the main potassium-modified products of the BRPH@MWCNT anode. In stark contrast, fully potassium-modified RP@MWCNT mainly exhibits K2P5. + K2P2 + and K5P4 + No K4P signal. + Or K3P + The presence of fragment ions confirms the failure of deep potassium conversion in RP@MWCNTs without heterostructure, consistent with electrochemical performance. TOF-SIMS three-dimensional depth profiling also validates the distribution of the major fragments, indicating a relatively uniform distribution. Figure 10b). Furthermore, a robust solid electrolyte layer (SEI) is crucial for highly reversible K redox reactions. To better understand the mechanism of improved cycling stability, the inventors investigated the surface composition of cycled BRPH@MWCNT and RP@MWCNT using XPS. The XPS F 1s spectrum of BRPH@MWCNT showed two distinct KF peaks at 683.6 and 682.0 eV. Figure 14 The KF intensity of the cycled RP@MWCNT is much weaker. The KF-rich SEI may be due to the strong built-in electric field at the heterojunction interface between BP and RP atoms inducing FSI in the electrolyte. - and TFSI - This is due to the decomposition of [the substance]. This indicates that by constructing abundant BP / RP heterostructures, the chemical composition of the SEI can be effectively regulated, parasitic reactions can be suppressed, and electrochemical reversibility can be enhanced.

[0086] Assembling potassium-ion full cells using elemental phosphorus anodes is a crucial step for practical applications, but it remains a significant challenge due to slow reaction kinetics and poor electrochemical reversibility. The inventors have successfully assembled a BRPH@MWCNT / Prussian blue full cell (N / P ratio 1.4:1). Figure 15 a). XRD patterns show that the synthesized Prussian blue cathode has a rhombic structure with R3′m spatial groups ( Figure 16 In the K metal / Prussian blue half-cell, it exhibits two characteristic discharge plateaus at 4.0 V and 3.9 V, with high rate capability ( Figure 17 Based on the total mass of the active materials on the positive and negative electrodes, the inventors' BRPH@MWCNT / Prussian Blue full cell achieves a mass of 100 mA g. -1 The specific capacity at that time was 76 mAh g. -1 ( Figure 15 (b and c). The excellent reaction kinetics of the BRPH@MWCNT anode ensure good rate performance of the full cell, providing up to 300 mA g. -1 High current density (2.5 C, Figure 15 c and Figure 18 In addition, at 300 mA g −1 After 100 cycles, it still retains 63% of its initial capacity. Figure 15 d) This indicates that the two electrodes possess high electrochemical reversibility. For comparison, the inventors also assembled an RP@MWCNT / Prussian blue full cell, and observed a sharp decrease in capacity during the first 40 cycles at an optimized N / P ratio of 1.3. Figure 19 Furthermore, even at a much lower N / P ratio of 1.1, the BRPH@MWCNT / Prussian full cell exhibits performance at 200 mA g. -1It retains 46% of its original capacity after 100 cycles. Figure 20 ).

[0087] Example 2

[0088] This embodiment relates to the synthesis of MWNT-loaded black phosphorus-red phosphorus heterostructure material and the performance testing of lithium batteries, with ethylenediamine as the phosphorus chain attacking agent.

[0089] In this embodiment, the synthesis of the MWCNT-supported black phosphorus-red phosphorus heterostructure material is the same as in Example 1. The battery performance of this embodiment is a half-cell, that is, with Li as the counter electrode and the BRPH@MWCNT synthesized in Example 1 as the lithium-ion battery anode, the lithium-ion storage performance is tested.

[0090] The 160°C-24h cycle performance of the half-cell in this embodiment is shown in [reference]. Figure 21 The electrolyte was 1M LiPF6 inEC DMC, and the current density was 100 mA g. -1 .Depend on Figure 21 It can be seen that using BRPH@MWCNT as the negative electrode of a lithium-ion battery has good cycle stability.

[0091] Example 3

[0092] This embodiment relates to the synthesis of MWNT-supported black phosphorus-red phosphorus heterostructure and its performance testing in a potassium-ion battery. The phosphorus chain attacking agent is a mixture of ethylenediamine and DMF, wherein the volume ratio of ethylenediamine to DMF is 1:1. To distinguish it from Examples 1 and 2, the carbon-supported black phosphorus-red phosphorus heterostructure obtained in this embodiment is abbreviated as BP / RP@MWCNT.

[0093] The synthesis method of this embodiment is similar to that of the red phosphorus-black phosphorus heterojunction material in Example 1. The solvothermal temperature is 120°C, the time is 24h, and the solvent composition is: ethylenediamine:DMF=1:1 v.

[0094] The prepared BP / RP@MWCNTs were characterized by SEM and HRTEM. The SEM characterization results are shown in [link to SEM description]. Figure 22 HRTEM characterization results and Figure 3 Similar to d. (By) Figure 22 It can be seen that in the synthesized BP / RP@MWCNT, the BP / RP grains grow alternately along the MWCNT axis.

[0095] The battery performance in this embodiment is a half-cell, that is, K is used as the counter electrode, and BP / RP@MWCNT synthesized in this embodiment is used as the negative electrode of the potassium-ion battery to test the potassium-ion storage performance.

[0096] For the cycle performance of the half-cell in this embodiment, please refer to [reference needed]. Figure 23 The electrolyte was a 1:1 v% ECDMC solution of 4M KFSI and 1M KTFSI, and the current density was 100 mA g. -1 .Depend on Figure 23 It can be seen that BP / RP@MWCNT has excellent cycle performance when used as a negative electrode for potassium-ion batteries.

[0097] Example 4

[0098] This embodiment relates to the synthesis of carbon fibers with a black phosphorus-red phosphorus heterostructure and the performance testing of sodium-ion batteries, with ethylenediamine as the phosphorus chain attacking agent. The synthesis method of the carbon fibers with the black phosphorus-red phosphorus heterostructure in this embodiment is similar to that in Example 1, except that MWNT is replaced with carbon fibers.

[0099] For ease of description, the carbon material prepared in this embodiment will be referred to as BP / RP@CF. The prepared BP / RP@CF was characterized by SEM and HRTEM; the SEM characterization results are shown in [link to SEM description]. Figure 24 HRTEM characterization results and Figure 3 Similar to d. (By) Figure 24 It can be seen that in the synthesized BP / RP@CF, the BP / RP grains grow alternately along the CF axis.

[0100] The prepared BP / RP@CF was also Raman-characterized; the characterization results are shown in [link to Raman characterization]. Figure 25 Raman spectroscopy confirmed BP (Ag1, B) 2g and A g 2 The peaks are located at 362.8, 444.7, and 470.0 cm. -1 The peaks for RP (B1, A1, and E1) are located at 350.1, 395.0, and 450.2 cm⁻¹, respectively. -1 )coexist.

[0101] The battery performance in this embodiment is a half-cell, that is, with Na as the counter electrode and BP / RP@MWCNT synthesized in this embodiment as the negative electrode of the potassium-ion battery, the sodium-ion storage performance is tested.

[0102] The charge / discharge curve of the half-cell in this embodiment is shown in [reference]. Figure 26 And its cycle performance is shown in [reference]. Figure 27 The electrolyte is a PY solution containing 2M NaFSI and 0.12M NaTFSI. 13 FSI solution, current density 100 mA g -1 .Depend on Figure 26 and 27 It can be seen that the BP / RP@CF negative electrode has low overpotential and long cycle life.

[0103] Example 5

[0104] This embodiment relates to the synthesis of carbon fibers with a black phosphorus-red phosphorus heterostructure and the performance testing of potassium-ion batteries. The phosphorus chain attacking agent is ethylenediamine. The synthesis method of BP / RP@CF in this embodiment is the same as that in Example 4.

[0105] The battery performance in this embodiment is a half-cell, that is, K is used as the counter electrode, and BP / RP@MWCNT synthesized in this embodiment is used as the negative electrode of the potassium-ion battery to test the potassium-ion storage performance.

[0106] For the rate performance of the half-cell in this embodiment, please refer to [link / reference]. Figure 28 The electrolyte is 1M KFSI in EC DMC. Figure 28 It can be seen that BP / RP@CF has good rate performance of potassium-ion batteries.

Claims

1. A carbon-supported black phosphorus-red phosphorus heterostructure material, characterized in that, Black phosphorus / red phosphorus grains grow alternately along the longitudinal axis of the carbon material, and each black phosphorus / red phosphorus grain includes at least two black phosphorus-red phosphorus heterostructures. The black phosphorus / red phosphorus crystals have a core-shell structure, with crystalline elemental black phosphorus forming the core and amorphous elemental red phosphorus forming the shell; the carbon material is carbon nanotubes or carbon fibers. The method for preparing the carbon-supported black phosphorus-red phosphorus heterostructure material includes subjecting red phosphorus, a phosphorus chain attacking agent, and carbon material to a solvothermal reaction to obtain the carbon-supported black phosphorus-red phosphorus heterostructure material; the reaction temperature of the solvothermal reaction is 120-180℃, and the reaction time is 12-48 hours.

2. A method for preparing a carbon-supported black phosphorus-red phosphorus heterostructure material as described in claim 1, characterized in that, The method involves subjecting red phosphorus, a phosphorus chain attacking agent, and a carbon material to a solvothermal reaction to obtain the carbon-supported black phosphorus-red phosphorus heterostructure material.

3. The preparation method according to claim 2, characterized in that, The method includes the following steps: S11: Pre-treat red phosphorus to remove residual oxides on the surface of red phosphorus and obtain loose red phosphorus; S12: The loose red phosphorus, the phosphorus chain attacking agent, and the carbon material are subjected to a solvothermal reaction to obtain the carbon-supported black phosphorus-red phosphorus heterostructure material.

4. The preparation method according to claim 2 or 3, characterized in that, The phosphorus chain attacking agent is ethylenediamine or a mixture of ethylenediamine and N,N-dimethylformamide.

5. The preparation method according to claim 2 or 3, characterized in that, The mass ratio of red phosphorus, phosphorus chain attack agent and carbon material is 7.5:216-108:1 by weight; the reaction conditions for the solvothermal reaction are: a closed reaction vessel.

6. The use of the carbon-supported black phosphorus-red phosphorus heterostructure material as described in claim 1 as a battery anode material.

7. A negative electrode, characterized in that, The negative electrode is made of a carbon-supported black phosphorus-red phosphorus heterostructure material as described in claim 1.

8. A rechargeable battery, characterized in that, Includes the negative electrode as described in claim 7.

9. The rechargeable battery as claimed in claim 8, characterized in that, The rechargeable battery is a lithium-ion battery, a sodium-ion battery, or a potassium-ion battery.

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