A method for preparing a gradient dual-phase polymer interfacial layer modified metal electrode and application thereof

Abstract

The application discloses a preparation method of a gradient two-phase polymer interface layer modified metal electrode. The gradient two-phase polymer interface layer modified metal electrode is prepared by coating a metal negative electrode with a mixed solution of PBI and PVA and then vacuum drying the metal negative electrode coated with the PBI and PVA mixture. The PBI and PVA mixture on the metal negative electrode is decomposed by spinodal to form a continuous gradient two-phase structure with loose upper and dense lower, which can realize multi-step coupling kinetics balance of mass transfer, reduction and nucleation in the zinc deposition process, and fundamentally inhibit the growth of dendrites. The zinc anode with the two-phase gradient polymer interface can be stably operated at 5 mA cm ‑2 for 7500 hours, reach about 92% of the zinc utilization rate in 10 mA cm ‑2 for 600 hours, and be stably operated at 40 mA cm ‑2 for 1500 hours.

Description

Technical Field

[0001] This invention relates to the field of aqueous zinc-ion batteries, specifically to a metal electrode modified with a gradient biphase polymer interface layer and its preparation method. Background Technology

[0002] Over-reliance on fossil fuels has triggered a severe environmental crisis, with global warming continuing to intensify and temperatures exceeding the limits set by the Paris Agreement, leading to a series of ecological and environmental problems. Against this backdrop, the replacement of fossil fuels with clean energy has become an inevitable trend. However, renewable energy sources such as wind and solar power have inherent drawbacks such as uneven spatial and temporal distribution and intermittent power supply, necessitating the development of efficient energy storage systems to address these issues. Lithium-ion batteries, due to their extremely high energy density, cycle life of thousands of charge-discharge cycles, and outstanding energy conversion efficiency, occupy a core position among various energy storage technologies. However, lithium-ion batteries also present inherent safety hazards that are difficult to eliminate, including electrochemical instability, volatility, leakage, and flammability.

[0003] To overcome the aforementioned bottlenecks of lithium-ion batteries, researchers have begun exploring next-generation energy storage systems. Aqueous zinc-ion batteries, using an aqueous solution as the electrolyte and zinc metal as the negative electrode, have shown great application potential and are expected to complement lithium-ion batteries. They are suitable for large-scale stationary energy storage scenarios with extremely high requirements for safety and cost. This is because: First, the aqueous electrolyte in aqueous zinc-ion batteries is non-flammable, fundamentally solving the battery's safety hazards. Second, zinc resources are abundant, inexpensive, and have mature mining and processing technologies; the battery materials are non-toxic, harmless, and easy to recycle. Additionally, the zinc metal negative electrode has a high theoretical capacity (theoretical specific capacity 820 mAh g⁻¹). -1 Or the theoretical volumetric capacity is 5855 mAh cm⁻¹ -3 And a suitable redox potential (-0.76 V vs. SHE).

[0004] Although aqueous zinc batteries offer significant advantages, the uncontrollable dendrite growth on the zinc metal anode limits their commercialization. Specifically, zinc metal electrodeposition involves two consecutive stages: nucleation and growth. During the nucleation stage, zinc ions (Zn...)... 2+ During initial deposition, Zn tends to preferentially reduce at sites with uneven energy distribution on the negative electrode surface (such as defects, scratches, and protrusions). Due to the uneven distribution of electrochemical active sites on the substrate itself, Zn... 2+Initial nucleation is difficult to achieve uniformity and density, instead forming dispersed nuclei of varying sizes. This uneven nucleation provides "seeds" for subsequent dendrite growth. During the growth stage, as deposition proceeds, due to the tip effect, the current density at the tip of the formed micro-protrusion is much higher than in other flat areas. According to the principle of electrodeposition, the higher the current density, the faster the rate of ion reduction and metal deposition. This causes zinc ions to preferentially accumulate and continuously deposit at the tip, leading to the rapid outward extension of the protrusion, forming needle-like or moss-like zinc dendrites. The continuous growth of dendrites not only leads to poor battery cycle stability but also exacerbates side reactions between zinc and aqueous electrolytes, reducing coulombic efficiency. More importantly, dendrites may pierce the battery separator, causing direct contact between the positive and negative electrodes and resulting in internal short circuits, leading to battery failure or even safety accidents. Therefore, developing a new zinc anode interface that can simultaneously regulate the balance of multiple kinetic processes, suppress dendrite growth, and improve the performance of aqueous zinc batteries is a major technical challenge for realizing the commercial application of aqueous zinc-ion batteries. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a gradient biphase polymer interface layer modified metal electrode and its preparation method. By coating a mixture of polybenzimidazole solution and polyvinyl alcohol solution onto a metal electrode, the polymer interface layer undergoes spontaneous spinodal decomposition to form a continuously interpenetrating gradient biphase structure, thereby significantly suppressing dendrite growth and improving the performance of aqueous zinc-ion batteries. The synthesis method of the gradient biphase polymer interface layer modified metal electrode provided by the present invention is specific and efficient, and its product exhibits both high dendrite suppression capability and high electrochemical stability.

[0006] To achieve the above objectives, the present invention first provides a method for preparing a metal electrode modified with a gradient biphase polymer interface layer, the method comprising the following steps: (1) Preparation of polybenzimidazole solution: Polybenzimidazole or its derivatives are dissolved in an organic solvent under an argon (Ar) atmosphere and stirred until completely dissolved to obtain a polybenzimidazole solution; (2) Preparation of polyvinyl alcohol (PVA) solution: Dissolve polyvinyl alcohol in an organic solvent and stir until completely dissolved to obtain a polyvinyl alcohol solution; (3) Preparation of metal electrodes modified with gradient biphase polymer interface layer: The polybenzimidazole solution obtained in step (1) and the polyvinyl alcohol solution obtained in step (2) are rapidly mixed and stirred until completely homogeneous. The resulting mixed solution is spin-coated onto the metal substrate at a speed of 1500~2000 rpm and vacuum dried to allow it to undergo spinodal decomposition and remove the organic solvent.

[0007] In one embodiment of the present invention, in step (1), the polybenzimidazole is a commercially available unmodified PBI powder, and the polybenzimidazole derivative is a terminally modified derivative, including any one or a combination of sulfonated PBI, carboxylated PBI, and PBI containing quaternary ammonium side chains, preferably unmodified PBI.

[0008] In one embodiment of the present invention, in step (1), the organic solvent is dimethyl sulfoxide, and the mass concentration of polybenzimidazole or its derivative in the polybenzimidazole solution is 0.01~0.10 g / mL, wherein the mass concentration refers to the mass-volume ratio of polybenzimidazole or its derivative to dimethyl sulfoxide (DMSO) in the solution, and the mass concentration is preferably 0.03~0.05 g / mL, more preferably 0.033 g / mL.

[0009] In one embodiment of the present invention, in step (1), the temperature at which the mixture is stirred until dissolved is 80~120°C, preferably 95°C; the stirring time is 6~30 h, preferably 24 h, to ensure that the PBI is completely dissolved and the system is clear. The dissolution operation is carried out in an anhydrous and oxygen-free environment (H2O, O2 content ≤10 ppm) or an inert atmosphere (N2 or Ar) to avoid the introduction of moisture affecting the subsequent phase separation behavior.

[0010] In one embodiment of the present invention, in step (2), the organic solvent is dimethyl sulfoxide (DMSO), and the mass concentration of polyvinyl alcohol (PVA) in the polyvinyl alcohol solution is 0.005~0.06 g / mL, preferably 0.02~0.03 g / mL, more preferably 0.02 g / mL, wherein the mass concentration refers to the mass-volume ratio of polyvinyl alcohol to organic solvent; the stirring temperature is 20~110℃, preferably 95℃ to ensure that the temperature is similar when mixing with the PBI solution, thereby eliminating the influence of temperature on uniform mixing; the stirring time is 1~10 h, preferably 3~5 h.

[0011] In one embodiment of the present invention, in step (3), the PBI solution and the PVA solution are mixed at a mass ratio of (20~90):(80~10), preferably (40~70):(60~30), more preferably (55~65):(45~35); wherein a PBI mass fraction of less than 20% may not be able to form an upper loose phase to reduce ion flux, and a mass fraction of more than 90% may not be able to form a gradient biphase polymer interface and make the whole into a network interface.

[0012] In one embodiment of the present invention, in step (3), the homogenization stirring time after mixing is 1~30 min, preferably 5~15 min; high-speed shearing (5000~15000 rpm, 30~180 s) or ultrasound (power 100~400 W, 1~5 min) can be used to promote initial homogeneity.

[0013] In one embodiment of the present invention, in step (3), the spin coating speed is 1000~3000 rpm, preferably 1500~2500 rpm, more preferably 2000 rpm; the spin coating time is 30 s~10 min, preferably 3~6 min.

[0014] In one embodiment of the present invention, in step (3), the thickness of the spin-coated film ranges from 0.1 to 10 μm, preferably from 0.5 to 3 μm, and more preferably from 1 to 2 μm. The thickness of the spin-coated film can be obtained by adjusting the total solid content and the spin-coating speed; the thickness deviation (1σ) is ≤10%.

[0015] In one embodiment of the present invention, in step (3), the spin-coated material is immediately transferred to a vacuum oven or an inert atmosphere hot table and dried at 60~90°C for 4~24 h. The drying temperature is preferably 70~80°C, more preferably 75°C, and the drying time is preferably 10~14 h. The vacuum degree is ≤200 Pa, preferably ≤100 Pa, so as to simultaneously achieve solvent removal and spinodal decomposition.

[0016] In one embodiment of the present invention, in step (3), programmed temperature rise (e.g., 25°C for 0.5-1 h → 50°C for 1-2 h → 75°C for the remaining time) is permitted to mitigate internal solvent retention caused by rapid surface film formation.

[0017] In one embodiment of the present invention, in step (3), the film thickness and gradient amplitude can be linearly adjusted by changing any two of the three factors of PBI:PVA ratio, total solid content and drying temperature, so as to achieve customization for different current density application requirements.

[0018] In one embodiment of the present invention, the metal substrate includes one of aluminum foil, zinc foil, copper foil, and magnesium foil. The gradient biphase polymer interface layer can also be applied to other secondary metal or ion batteries, including but not limited to zinc-ion batteries, sodium-ion batteries, potassium-ion batteries, magnesium / aluminum multivalent metal batteries, and their all-solid-state or gel-state forms. In these applications, the gradient biphase polymer interface can serve as: 1) a protective / regulating layer on the surface of the metal anode; 2) a bonding / buffer transition layer between the separator (or solid electrolyte sheet) and the anode; 3) a surface functionalized coating of the composite current collector or functional separator; and 4) an interface matching layer between the ceramic / polymer composite electrolyte and the metal anode in an all-solid-state battery.

[0019] The present invention also discloses a metal electrode modified with a gradient biphase polymer interface layer prepared according to the above method, wherein the metal electrode is preferably a zinc metal electrode.

[0020] In one embodiment of the present invention, in the gradient biphase polymer interface modified metal electrode, the interface layer near the metal side is a dense layer rich in PVA, and away from the metal side is a loose layer rich in PBI, forming an overall gradient structure from a loose PBI layer to a dense PVA layer from top to bottom. This structure enables a multi-step coupled kinetic balance of mass transfer, reduction, and nucleation during zinc deposition, thereby fundamentally suppressing dendrite growth. The zinc anode using the biphase gradient polymer interface can achieve a deposition rate of 5 mA cm⁻¹. -2 Achieve stable operation for 7500 hours at 10 mA cm⁻¹ -2 10.8 mAh cm -2 It achieves approximately 92% zinc utilization within the next 600-hour cycle and at 40 mA cm⁻¹ -2 It exhibits stable operation for 1500 hours under high current.

[0021] Beneficial effects: (1) This invention selects two polymers, PBI and PVA, which have different solubilities, polarities, and hydrogen bonding capabilities. After homogenizing the solutions of the two polymers, they are spin-coated onto a metal electrode. Vacuum drying is used to promote the spontaneous spinodal decomposition of the polymers, forming a continuous interpenetrating gradient two-phase structure. This structure can achieve a multi-step coupled kinetic balance of mass transfer, reduction, and nucleation during zinc deposition, thereby fundamentally inhibiting dendrite growth. The preparation process uses PBI / PVA solution mixing to induce spontaneous spinodal decomposition and in-situ film formation. It does not require sacrificial templates, complex etching, or vacuum deposition. It has fewer steps, lower energy consumption, and can be scaled up roll to roll. The raw materials are widely available, inexpensive, and environmentally friendly (avoiding strong corrosive / fluorinated reagents), and have significant advantages in terms of scale and cost, lowering the threshold for industrialization.

[0022] (2) The biphase gradient polymer interface layer provided by the present invention transforms the mass transfer kinetics, reduction kinetics and nucleation kinetics from a coupled imbalance state to a synergistic matching state, thereby achieving synchronous control of the entire metal deposition process, suppressing dendrite formation and its self-catalytic amplification chain from the source, and meeting the practical application requirements of high current density and high zinc utilization.

[0023] (3) The interface layer of the present invention forms a continuously interpenetrating gradient two-phase structure through spontaneous spinodal decomposition, constructing three synergistic functional domains: Zn on the electrolyte / interface side. 2+ Enrichment domain enhances local Zn 2+ Concentration and suppression of excessively thick diffusion layers; the upper PBI enriched porous selective conduction domain synergistically weakens the hydration shell structure through polar / coordinating groups such as -C=N and -NH, reducing Zn concentration. 2+ Desolvation of the solubility barrier provides a fast directional transport channel; the lower PVA dense redistribution domain enables lateral diffusion acceleration of Zn with uniformly distributed zinc affinity sites. 2+ Mass transfer process. In addition, the zinc-loving sites provided by the dense layer, combined with the acceleration effect of the entire interface on mass transfer, realize a hybrid optimal nucleation mode of "instantaneous + gradual", thereby obtaining a uniform, dense and flat metal deposition layer.

[0024] (4) Compared with single-function network / porous artificial layer, the interface layer of the present invention can simultaneously regulate the Zn in the bulk electrolyte. 2+ The continuous coupling steps of migration → near-interface enrichment / desolvation → surface self-diffusion / nucleation overcome the inherent limitation of existing protective layers that "only improve one aspect and are difficult to synchronize," and avoid the transformation from initial microscale non-uniform nucleation to later dendritic autocatalytic acceleration.

[0025] (5) The zinc anode of the present invention using a two-phase gradient polymer interface can achieve a speed of 5 mA cm⁻¹ -2 Stable operation for 7500 hours at 10 mA cm -2 10.8 mAh cm -2 After 600 hours of cycling, approximately 92% zinc utilization was achieved, and at 40 mA cm⁻¹ -2 It operated stably for 1500 hours under high current without any signs of runaway dendrites or short circuits.

[0026] (6) The gradient two-phase control strategy of the present invention has universal scalability and can be transferred to various positive electrode systems such as Zn||air and Zn||V2O5. It can also provide an interface control paradigm for other metal negative electrodes such as Li, Na and K, and has broad application prospects. Attached Figure Description

[0027] Figure 1 This is a scanning electron microscope image of the surface of the zinc metal anode modified with the gradient biphase (GBP) polymer interface layer in Example 1. Figure 2 This is a cross-sectional scanning electron microscope image of the zinc metal anode modified with the GBP polymer interface layer in Example 1; Figure 3 This is a graph showing the surface energy dispersive spectroscopy (SED) results of the zinc metal anode modified with the GBP polymer interface layer in Example 1. Figure 4 The X-ray photoelectron spectroscopy (XPS) depth profile of the zinc metal anode modified with the GBP polymer interface layer in Example 1 is shown. Figure 5 Electronic photographs showing the obvious morphological differences between the GBP film and the pure PVA / PBI film in Example 1; Figure 6 The GBP@Zn / GBP@Zn symmetric cell of Example 1 was tested at 5 mA cm⁻¹. -2 1 mAh cm -2 The following is a graph showing the cyclic performance. Figure 7 The GBP@Zn / GBP@Zn symmetric cell of Example 1 was tested at 10 mA cm⁻¹. -2 10.8 mAh cm -2 Cyclic performance diagram at 92% zinc utilization rate; Figure 8 The GBP@Zn / GBP@Zn symmetric cell of Example 1 was tested at 40 mA cm⁻¹. -2 2 mAh cm -2 Cyclic performance diagram at ultra-high current density. Detailed Implementation

[0028] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0029] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0030] I. General Instructions for the Preparation and Characterization of GBP (gradient bi-phase) Polymer Interfacial Layer Zinc Anodes Basic principles The GBP gradient biphase interface layer zinc anode proposed in this invention constructs a continuous gradient on the surface of a metal (e.g., Zn, Mg, Al) substrate by mixing two polymers with different solubilities, polarities, and hydrogen bonding capabilities (e.g., N-rich PBI containing heterocyclic aromatic structures and O-rich PVA containing a large number of hydroxyl groups) in a suitable solvent system (e.g., DMSO). This is achieved through controlled solvent removal and spontaneous spinodal decomposition, creating a layer that is "dense at the bottom + loose porous at the top." The interface layer undergoes spontaneous spinodal decomposition to form a continuously interpenetrating gradient biphase structure, constructing three synergistic functional domains: the electrolyte / interface side Zn... 2+ Enrichment domain enhances local Zn 2+ Concentration, inhibition of excessively thick diffusion layer (-C=N, -NH, -OH on the entire [Zn(H2O)5(SO4)2] 2- )] 2+ The attractiveness of the solvation group); the upper PBI enriched porous selective conduction domain weakens the hydration shell structure through the synergistic weakening of Zn by polar / coordinating groups such as -C=N and -NH, reducing the Zn content. 2+ Desolvation of the solubility barrier provides a fast directional transport channel; the lower PVA dense redistribution domain enables lateral diffusion acceleration of Zn with uniformly distributed zinc affinity sites. 2+ Mass transfer process. In addition, the zinc-loving sites provided by the dense layer, combined with the acceleration effect of the entire interface on mass transfer, realize a hybrid optimal nucleation mode of "instantaneous + gradual", thereby obtaining a uniform, dense and flat metal deposition layer.

[0031] Mechanism characteristics (1) Due to the difference in transient interdiffusion and phase separation kinetics between PBI and PVA during the high-temperature solvent removal process, a bottom-up composition and pore gradient is formed.

[0032] (2) The lower O-rich (PVA slightly enriched) region is an ultra-thin (about 10 nm) dense skin layer, which can suppress local ion flow "spiking"; the upper N-rich (PBI enriched) loose domain (about 2 μm) provides ion storage and stress release.

[0033] (3) The element (N→O) gradient and the pore structure gradient work together to achieve stable deposition and high metal utilization under high current density and high zinc utilization.

[0034] II. GBP Interface Layer Structure and Performance Testing Methods Morphology and thickness characterization (SEM) The processed samples were observed on their surface and cross-section under a scanning electron microscope. Cross-section preparation could be achieved using cryo-sectioning or low-energy beam sectioning. Record: pore size distribution of the upper loose phase, thickness of the lower dense phase, and overall film thickness.

[0035] Element distribution and gradient verification (EDS surface scan / line scan) Energy dispersive spectroscopy was performed to compare the changes in loose and dense morphologies of N (PBI marker element) and O (PVA marker element).

[0036] XPS In-Depth Analysis Using Ar + The sputtering process was analyzed stepwise (sputtering time-depth calibration) to examine the changes in the relative atomic ratios of C, N, and O over sputtering time.

[0037] Symmetrical battery assembly and cycle testing (1) Electrode preparation: After mechanically lightly polishing or chemically deoxidizing bare metal sheets (Zn, Mg, Al) (100 µm and 20 µm, 20 µm is only used for utilization testing), immediately spin-coat the obtained precursor solution in an inert atmosphere or dry air (e.g., rapid wetting with 0.5 mol / L HCl-rinsing with deionized water-drying).

[0038] (2) Diaphragm: Glass fiber (Whatman GF / D).

[0039] (3) Electrolyte: In the examples, 2.0 M ZnSO4, 2.0 M Zn(CF3SO3)2, mixed salt 1.5 M ZnSO4 + 0.5 M Zn(TFSI)2, or 2.0 M MgCl2, or 2.0 M Al(OTf)3 were selected respectively.

[0040] (4) Testing procedure: Constant current stripping (e.g., 5 mA cm⁻¹) -2 / 1 mAh cm -2 10 mA cm -2 / 10.8 mAhcm -2 40 mA cm -2 / 2 mAh cm -2 The lifetime is determined by the occurrence of a short circuit (sudden drop to near 0 V) ​​or the polarization continuously rising to a set threshold.

[0041] (5) Calculation of metal utilization rate (e.g., zinc utilization rate):

[0042] Among them, C actual (mAh g) -1 C is the actual specific capacity of the deposited / exfoliated metal. theoretical (mAh g) -1 The theoretical specific capacity of the metal anode is ~819 mAh g⁻¹. -1 ), I (mA cm -2) is the current density during the electroplating / stripping process, t (h) is the metal deposition / stripping time, and S (cm) is the current density during the deposition / stripping process. 2 ) and m(g) are the actual area and mass of the electrode, respectively.

[0043] Example 1 A method for preparing a zinc metal anode modified with a functionally graded biphase (GBP) polymer interface layer includes the following steps: (1) Preparation of PBI solution: Take 0.50 g of unmodified commercial PBI powder, add it to 15 mL of DMSO, and stir magnetically for 24 h at 95℃ under an argon atmosphere until clear (mass-volume ratio 0.033 g / mL) to obtain PBI solution.

[0044] (2) Preparation of PVA solution: 0.30 g of PVA was added to 15 mL of DMSO and stirred at 95℃ for 4 h (0.02 g / mL) to obtain PVA solution.

[0045] (3) Mixing: PBI solution obtained in step (1) and PVA solution obtained in step (2) are rapidly mixed at 95°C according to (solid mass in solution) PBI:PVA=60:40, followed by magnetic stirring for 10 min to remove bubbles (short-path nitrogen blowing to remove water).

[0046] (4) Spin coating: Place the Zn foil after deoxidation on a spin coating platform and spin coat the mixed solution obtained in step (3) at 2000 rpm for 5 min to obtain a wet film.

[0047] (5) Gradient / drying: The wet film obtained in step (4) is immediately transferred to a vacuum oven at 75°C (≤100 Pa) and dried for 12 h. Solvent removal and spontaneous spinodal decomposition are carried out simultaneously to form a gradient structure from top (away from Zn) to bottom (close to Zn) PBI-enriched loose layer → PVA-enriched dense layer.

[0048] The surface microstructure of the GBP polymer interface layer was observed using scanning electron microscopy (SEM), and the results are as follows: Figure 1 As shown, Figure 1 The GBP polymer interface layer synthesized using the above preparation method exhibits a biphase structure with a dense lower end superimposed on a loose upper end.

[0049] The cross-sectional microstructure of the GBP polymer interface layer was observed using scanning electron microscopy (SEM), and the results are as follows: Figure 2 As shown, Figure 2 The GBP polymer interface layer synthesized using the above preparation method exhibits an ultra-thin and dense structure (~10 nm) at the lower end superimposed with a loose two-phase structure (~2 μm) at the upper end.

[0050] The elemental distribution in the GBP polymer interface layer was observed using energy dispersive spectroscopy (EDS), and the results are as follows: Figure 3 As shown, in the GBP polymer interface layer prepared by the above synthesis method, the upper circular loose phase is mainly PBI rich in N elements, while the lower dense phase is mainly PVA rich in O elements.

[0051] X-ray photoelectron spectroscopy (XPS) was used for in-depth analysis to observe the elemental distribution from top to bottom in the GBP polymer interface layer. The results are as follows: Figure 4 As shown, the GBP polymer interface layer synthesized by the above preparation method exhibits a gradient structure with N elements gradually decreasing and O elements gradually increasing from top to bottom.

[0052] Through actual film formation comparison, the obvious morphological differences between GBP film and pure PVA / PBI film control were observed. Figure 5 This further confirms the existence of this gradient biphase structure.

[0053] Electrochemical measurements were performed using CR2032 coin cells and pouch cells assembled in air. Bare Zn and GBP@Zn electrodes were pressed into a disk. Symmetrical cells were assembled using glass fiber (Whatman GF / D) as the separator and 2 M ZnSO4 aqueous solution as the electrolyte.

[0054] After testing, such as Figure 6 As shown, GBP@Zn / GBP@Zn (5 mA cm⁻¹) -2 1 mAh cm -2 The overpotential of the symmetrical cell was 15±3 mV, and it remained stable for 7500 h without dendrite short circuits. Figure 7 As shown, GBP@Zn / GBP@Zn (10 mA cm⁻¹) -2 10.8 mAh cm -2 Under conditions where zinc utilization reaches 92.0%, stable cycling for 600 hours showed no short circuit caused by dendrites. Figure 8 As shown, GBP@Zn / GBP@Zn at 40 mA cm⁻¹ -2 2 mAh cm -2 It can remain stable for 1500 hours under ultra-high current without dendrite-induced failure.

[0055] Example 2 The difference between Example 2 and Example 1 is that the electrolyte is changed to a 2.0 M Zn(CF3SO3)2 aqueous solution.

[0056] Tests showed that the GBP@Zn / GBP@Zn symmetric cell operates at 5 mA cm⁻¹. -2 1 mAh cm-2 The system can be stably cycled for 6800 hours with a 92% zinc utilization rate (10 mA cm⁻¹). -2 10.8 mAh cm -2 It ran for 500 hours under ultra-high current density of 40 mA cm⁻¹. -2 2mAh cm -2 It ran for 1600 hours.

[0057] Example 3 The difference between Example 3 and Example 1 is that a mixed salt electrolyte of 1.5 M ZnSO4 + 0.5 M Zn(TFSI)2 was used.

[0058] Tests showed that the GBP@Zn / GBP@Zn symmetric cell operates at 5 mA cm⁻¹. -2 1 mAh cm -2 Under stable cycling conditions for 7200 hours, with a zinc utilization rate of 92% (10 mA cm⁻¹). -2 10.8 mAh cm -2 It ran for 200 hours under ultra-high current density of 40 mA cm⁻¹. -2 2mAh cm -2 Run for 1000 hours.

[0059] Example 4 The difference between Example 4 and Example 1 is that the magnesium foil after deoxidation is used to replace the Zn foil after deoxidation in step (4), the electrolyte is 2 M MgCl2, the cathode is MnO2, and the diaphragm is Whatman GF / D glass fiber diaphragm.

[0060] Tests showed that the GBP@Mg / GBP@Mg symmetric cell operated at 5 mA cm⁻¹ -2 1 mAh cm -2 Under stable cycling conditions for 5000 hours, with a magnesium utilization rate of 92% (10 mA cm⁻¹). -2 10.8 mAh cm -2 It ran for 200 hours under ultra-high current density of 40 mA cm⁻¹. -2 2mAh cm -2 It ran for 1200 hours.

[0061] Example 5 The difference between Example 5 and Example 1 is that the aluminum foil after deoxidation is used to replace the Zn foil after deoxidation in step (4), the electrolyte is 2.0 M Al(OTf)3, the cathode is MnO2, and the diaphragm is Whatman GF / D glass fiber diaphragm.

[0062] Tests showed that the GBP@Al / GBP@Al symmetric cell operates at 5 mA cm⁻¹ -2 1 mAh cm -2 Under stable cycling conditions for 8000 hours, with 92% aluminum utilization (10 mA cm⁻¹) -2 10.8 mAh cm -2 It ran for 240 hours under ultra-high current density of 40 mA cm⁻¹. -2 2mAh cm -2 It ran for 700 hours.

[0063] Example 6 The difference between Example 6 and Example 1 is that only 0.50g of 10 wt% carboxylated PBI derivative (10 wt% polyacrylic acid grafted PBI) was used to replace the commercial PBI powder in step (1), and the overall thickness of the gradient film was 2 μm.

[0064] The preparation method of polyacrylic acid grafted PBI includes the following steps: (1) Add 1.80 g PBI to 40 mL DMSO and stir overnight at 95°C until clear; cool to 50°C and deoxygenate the solution by argon bubbling for 30 min.

[0065] (2) Preparation of acrylic acid solution: 0.24 g of acrylic acid is prepared into a 20 wt% solution with a small amount of DMSO.

[0066] (3) At 50°C and under an inert atmosphere, acrylic acid solution was slowly added dropwise (to be completed in 30 min), and 5 mLAPS (ammonium persulfate) and NaHSO3 mixed initiator were added in 4 portions (to be completed within 1 h). The concentrations of APS and NaHSO3 in the mixed initiator were both 0.1 M.

[0067] (4) Maintain the reaction at 55°C for a total of 4 hours with stirring.

[0068] (6) After the reaction solution is cooled, it is slowly poured into a water / ethanol = 1 / 1 mixture to precipitate; the precipitate is collected by filtration / centrifugation, and washed repeatedly with water and ethanol; the product is obtained by vacuum drying at 60℃ for 24 h.

[0069] Tests showed that the GBP@Zn / GBP@Zn symmetric cell operates at 5 mA cm⁻¹. -2 1 mAh cm -2 It can be stably cycled for 7500 hours with 92% aluminum utilization (10 mA cm⁻¹). -2 10.8 mAh cm -2 It ran for 400 hours under ultra-high current density of 40 mA cm⁻¹. -2 2mAh cm -2 Run for 500 hours.

[0070] Example 7 The difference between Example 7 and Example 1 is that 0.30g of carboxymethylated PVA derivative (CM-PVA) was used to replace the commercial PVA powder in step (1), and the overall thickness of the gradient film was 2 μm.

[0071] The preparation method of CM-PVA includes the following steps: (1) Add 5.0 g PVA to 95 mL of water and stir at 95°C until clear; then cool to 60°C.

[0072] (2) Add 30 wt% NaOH (total NaOH≈3.0 g, about 8 mL), keep pH 12, and stir at 60°C for 15 min.

[0073] (3) Prepare a 30wt% solution of 3.0 g monochloroacetic acid MC and add it in batches to the solution in step (2). Maintain the pH at 11.5 with a small amount of NaOH and maintain the reaction at 60°C for 4 h. After the reaction, cool to room temperature and adjust the pH to 7.

[0074] (4) Pour the mixture from step (3) into 10 times the volume of cold ethanol to precipitate; collect by filtration / centrifugation and wash with ethanol 3 times.

[0075] (5) Vacuum drying at 50℃ for 24 h yielded CM-PVA powder.

[0076] Tests showed that the GBP@Zn / GBP@Zn symmetric cell operates at 5 mA cm⁻¹. -2 1 mAh cm -2 It can be stably cycled for 8200 hours with 92% aluminum utilization (10 mA cm⁻¹). -2 10.8 mAh cm -2 It ran for 500 hours under ultra-high current density of 40 mA cm⁻¹. -2 2mAh cm -2 It runs for 800 hours.

[0077] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the spin coating speed in step (4) is 3000 rpm.

[0078] (1) Preparation of PBI solution: Take 0.50 g of unmodified commercial PBI powder, add it to 15 mL of DMSO, and stir magnetically for 24 h at 95℃ under an argon atmosphere until clear (mass-volume ratio 0.033 g / mL) to obtain PBI solution.

[0079] (2) Preparation of PVA solution: Take 0.30 g PVA (Mw≈85–124 k) and add it to 15 mL DMSO. Stir at 95℃ for 4 h (0.02 g / mL) to obtain PVA solution.

[0080] (3) Mixing: PBI solution obtained in step (1) and PVA solution obtained in step (2) are rapidly mixed at 95°C according to (solid mass in solution) PBI:PVA=60:40, followed by magnetic stirring for 10 min to remove bubbles (short-path nitrogen blowing to remove water).

[0081] (4) Spin coating: Place the Zn foil after deoxidation on a spin coating platform and spin coat the mixed solution obtained in step (3) at 3000 rpm for 5 min to obtain a wet film.

[0082] (5) Gradient / drying: The wet film obtained in step (4) is immediately transferred to a vacuum oven at 75°C (≤100 Pa) and dried for 12 h. Solvent removal and spontaneous spinodal decomposition are carried out simultaneously to form a gradient structure from top (away from Zn) to bottom (close to Zn) PBI-enriched loose layer → PVA-enriched dense layer.

[0083] The results showed that the GBP layer prepared by this method was not uniform on the zinc anode surface, and the Zn / Zn symmetric cell was incompatible with the 5 mA cm⁻¹ method. -2 1 mAh cm -2 Under certain conditions, it can only cycle for 300 hours.

[0084] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the spin coating rate in step (4) is 1000 rpm, and the interface layer is significantly thickened (~5 μm).

[0085] The results showed that an excessively thick interface layer Zn 2+ The significantly reduced transport kinetics greatly affect electrochemical performance, particularly in Zn / Zn symmetric cells at 5 mA cm⁻¹. -2 1 mAh cm -2 Under these conditions, it can only cycle for 200 hours and the polarization voltage is very high.

[0086] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that step (2) is omitted, and only the PBI solution in step (1) is used for spin coating (solid content 0.033 g / mL) with a thickness of 2 μm.

[0087] The results showed that the dense PVA layer Zn was lacking. 2+ Mass transfer acceleration is limited and nucleation behavior is completely untunable. Dendrites cannot be effectively suppressed, and Zn / Zn symmetric cells at 5 mA cm⁻¹ exhibit poor performance.-2 1 mAh cm -2 Under the conditions of 25 mV overpotential, 3000 h lifetime, and 92% zinc utilization (10 mA cm⁻¹), the following parameters are achieved. -2 10.8 mAh cm -2 It ran for 500 hours under ultra-high current density of 40 mA cm⁻¹. -2 2 mAhcm -2 It is completely unusable.

[0088] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that step (1) is omitted, and only the PVA solution in step (2) is used for spin coating (0.02 g / mL) with a thickness of 2 μm.

[0089] The results showed that the PVA layer was too dense with Zn. 2+ Slow migration kinetics, Zn / Zn symmetric cells at 5 mA cm⁻¹ -2 1 mAhcm -2 Under the given conditions, the overpotential is 40 mV, the lifetime is 1000 h, and the zinc utilization rate is 92% (10 mA cm⁻¹). -2 10.8 mAh cm -2 Running for 100 hours at an ultra-high current density of 40 mA cm⁻¹ -2 2 mAh cm -2 It is completely unusable.

[0090] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that the drying temperature in step (5) is 110°C and the drying time is 6 hours.

[0091] The results showed that a dense, glassy film formed rapidly on the surface, followed by wetting, blistering, and cracking; the Zn / Zn symmetric cell exhibited a performance of 5 mA cm⁻¹. -2 1 mAh cm -2 It failed after 600 hours under the given conditions. This indicates that excessively rapid solvent removal disrupted the gradual phase separation.

[0092] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that in step (3), PBI:PVA = 15:85.

[0093] The results showed that after spin-coating using the same process as in Example 1, the thickness of the polymer interface layer was 1.4 μm, with a dense barrier layer formed by PVA-rich material at the bottom, resulting in low ion flux; the Zn / Zn symmetric cell achieved a flux of 5 mA cm⁻¹. -2 1 mAh cm -2Failure occurred after 1400 hours under these conditions. This indicates that a low proportion of disrupted two-phase gradients leading to the formation of a dense layer negatively impacts battery performance.

[0094] Comparative Example 7 The difference between Comparative Example 7 and Example 1 is that in step (3), PBI:PVA = 90:10.

[0095] The results showed that the measured film thickness was 1.6 μm, but the cross-section revealed an approximate single-phase continuous network with a lack of clear gradients; the Zn / Zn symmetric cell operated at 5 mA cm⁻¹. -2 1 mAh cm -2 Failure occurred after 1100 hours under these conditions. This indicates that a high proportion of disruption of the two-phase gradient negatively impacts battery performance.

[0096] Comparative Example 8 The difference between Comparative Example 8 and Example 1 is that NMP was used instead of DMSO when dissolving PBI and PVA. Specifically, 0.5 g of PBI was dissolved in 15 mL of NMP at 95°C and reacted for 24 h, and 0.3 g of PVA was dissolved in 15 mL of NMP.

[0097] The results showed that PBI could not completely dissolve, resulting in undissolved particles. After mixing, a large viscosity gradient was observed, and the spin-coated film exhibited flow marks and 2–5 μm pores. After drying at 75 °C for 12 h, microscopic examination revealed irregular nucleated phase separation (an island structure rather than a continuous two-phase structure). Zn / Zn symmetric cells were tested at 5 mA cm⁻¹. -2 1 mAh cm -2 It failed after 300 hours under the specified conditions. This indicates that an unsuitable solvent reduced the controllable decomposition window of spinodal.

[0098] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for preparing a metal electrode modified with a gradient biphase polymer interface layer, characterized in that, The method includes the following steps: (1) Preparation of polybenzimidazole solution: Polybenzimidazole or its derivatives are dissolved in dimethyl sulfoxide under an argon atmosphere and stirred until completely dissolved to obtain polybenzimidazole solution; (2) Preparation of polyvinyl alcohol solution: Polyvinyl alcohol is dissolved in dimethyl sulfoxide and stirred until completely dissolved to obtain a polyvinyl alcohol solution; (3) Preparation of graded biphase polymer interface layer modified metal electrode: The polybenzimidazole solution obtained in step (1) and the polyvinyl alcohol solution obtained in step (2) are mixed and stirred until completely homogeneous. The resulting mixed solution is spin-coated onto a metal substrate and vacuum dried to obtain a graded biphase polymer interface layer modified metal electrode. The mass ratio of the polybenzimidazole solution to the polyvinyl alcohol solution is (40~70):(60~30), and the stirring time after mixing is 1~30 min. The spin-coating speed is 1500~2500 rpm, and the spin-coating time is 30 s~10 min. The vacuum drying temperature is 60~90℃, the drying time is 4~24 h, and the vacuum degree is ≤200 Pa. The metal substrate includes one of aluminum foil, zinc foil, and magnesium foil.

2. The preparation method according to claim 1, characterized in that, In step (1), the polybenzimidazole derivative is a terminally modified derivative, including any one or a combination of several of sulfonated PBI, carboxylated PBI, and PBI containing quaternary ammonium side chains. The mass concentration of polybenzimidazole or its derivative in the polybenzimidazole solution is 0.01~0.10 g / mL. The temperature at which the solution is stirred until completely dissolved is 80~120℃, and the stirring time is 6~30 h.

3. The preparation method according to claim 1, characterized in that, In step (2), the mass concentration of polyvinyl alcohol in the polyvinyl alcohol solution is 0.005~0.06 g / mL; the stirring temperature is 20~110℃, and the stirring time is 1~10 h.

4. The preparation method according to claim 1, characterized in that, In step (3), high-speed shearing or ultrasonic-assisted stirring is used during mixing. The high-speed shearing speed is 5000~15000 rpm and the shearing time is 30~180 s. The ultrasonic power is 100~400 W and the ultrasonic time is 1~5 min.

5. The preparation method according to claim 1, characterized in that, In step (3), the thickness of the spin-coated film ranges from 0.1 to 10 μm.

6. A gradient biphase polymer interface layer modified metal electrode prepared by the method according to any one of claims 1 to 5.

7. The application of the gradient biphase polymer interface layer modified metal electrode according to claim 6 in a battery, wherein the battery includes one of an aluminum-ion battery, a zinc-ion battery, and a magnesium-ion battery.

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