Supramolecular proton battery electrolyte, preparation method and application thereof

Abstract

The application discloses a kind of supramolecular proton battery electrolyte and its preparation method and application, belong to the technical field of proton battery.The proton battery electrolyte is the electrolyte of pyrophosphoric acid-alpha-cyclodextrin supramolecular inclusion structure, and is made by mixing pyrophosphoric acid, alpha-cyclodextrin and deionized water.The electrolyte utilizes the hydrophobic cavity of alpha-cyclodextrin and the host-guest inclusion compound formed by pyrophosphoric acid molecule, simultaneously through the hydrogen bond network of electrolyte reconstruction by the outer wall hydroxyl of alpha-cyclodextrin, realizes proton slow-release effect and interface adsorption stability effect.The electrochemical stability window of the supramolecular electrolyte is widened to ≥3.6 V, water activity is significantly reduced, and hydrogen evolution side reaction is effectively inhibited.The water-based proton battery based on the electrolyte has a capacity retention rate of 70% after 10,000 cycles at a high current density of 5 A·g ‑1 The discharge specific capacity reaches 171 mAh·g ‑1 , with high specific capacity, long cycle life and high safety advantages.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage technology, and relates to a supramolecular proton battery electrolyte, its preparation method and application, specifically to an aqueous proton battery electrolyte based on the supramolecular interaction between pyrophosphate and α-cyclodextrin, its preparation method and application. Background Technology

[0002] With the surge in demand for renewable energy grid connection, the development of safe, low-cost, and long-life electrochemical energy storage systems has become a research hotspot. Aqueous proton batteries, using protons as charge carriers, possess advantages such as small ionic radius, fast Grotthuss conduction mechanism, high theoretical power density, and good intrinsic safety, demonstrating great potential in the field of large-scale energy storage.

[0003] However, traditional aqueous proton battery electrolytes have significant drawbacks: when using dilute sulfuric acid or pure phosphoric acid as electrolytes, the high activity of free water molecules results in a narrow electrochemical stability window, leading to severe hydrogen evolution and oxygen evolution reactions and exacerbating electrode material corrosion and dissolution. While ionic liquids or gel electrolytes can broaden the voltage window, they suffer from high interfacial impedance, poor low-temperature performance, and high cost. Furthermore, although pure pyrophosphate electrolytes have a relatively wide thermodynamic stability window, their high viscosity, poor fluidity, strong corrosiveness to electrodes, and high proton concentration leading to low overpotential limit their practical application.

[0004] Supramolecular chemistry offers a new approach to solving these problems. α-Cyclodextrin (α-CD) is a cyclic oligosaccharide composed of six D-glucan units linked by α-1,4-glycosidic bonds, possessing a unique structure with a hydrophobic inner cavity and a hydrophilic outer wall. This structure allows it to form host-guest inclusion complexes with molecules of specific sizes through van der Waals forces, hydrogen bonds, and hydrophobic interactions, thereby altering the chemical environment and reactivity of the guest molecules. Pyrophosphate, as a condensed phosphoric acid, has high proton dissociation capacity and viscosity. The molecular size of pyrophosphate matches the cavity of α-cyclodextrin, and the two can form an inclusion structure through host-guest recognition. Simultaneously, the hydroxyl groups on the outer wall of α-cyclodextrin can act as hydrogen bond donors / acceptors, reconstructing the hydrogen bond network with pyrophosphate and water molecules, thereby "anchoring" active water molecules, reducing water activity, and inducing the formation of ordered proton transport channels.

[0005] Based on this, this patent is dedicated to developing a supramolecular proton battery electrolyte based on pyrophosphate-α-cyclodextrin. By reconstructing the intermolecular hydrogen bond network to optimize the proton conduction pathway, α-cyclodextrin molecules are adsorbed on the electrode surface to form a dynamic supramolecular protective layer, which inhibits electrode corrosion and dissolution, enabling the proton battery to exhibit ultra-long cycle stability. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a pyrophosphate-α-cyclodextrin supramolecular electrolyte. This electrolyte solves the technical problems of severe hydrogen evolution, strong corrosiveness, and high viscosity in pure pyrophosphate electrolyte through the synergistic effect of supramolecular inclusion and hydrogen bond network reconstruction, while also addressing the narrow electrochemical window of traditional dilute acid electrolytes.

[0007] To achieve the above-mentioned objective, the first aspect of the present invention provides a supramolecular proton battery electrolyte, wherein the proton battery electrolyte is a pyrophosphate-α-cyclodextrin electrolyte, which is prepared by mixing pyrophosphate, α-cyclodextrin and deionized water.

[0008] Further, in molar ratio, pyrophosphate: α-cyclodextrin: deionized water = 1:(0.002 - 0.012):(2.5 - 4.0).

[0009] Furthermore, the molar ratio of pyrophosphate : α-cyclodextrin : deionized water is 1 : 0.0073 : 2.74.

[0010] Furthermore, the purity of the pyrophosphate is ≥95 wt%.

[0011] A second aspect of the present invention provides a method for preparing a proton battery electrolyte, the method comprising: mixing α-cyclodextrin with deionized water, stirring at 300 r / min - 500 r / min until the α-cyclodextrin is completely dissolved to obtain an α-cyclodextrin aqueous solution; preheating pyrophosphoric acid in a water bath at 40 °C - 60 °C for 20 min - 40 min to obtain a fluidized state of pyrophosphoric acid; slowly adding the α-cyclodextrin aqueous solution to the fluidized state of pyrophosphoric acid, stirring and ultrasonically mixing, and cooling to room temperature to obtain a pyrophosphoric acid-α-cyclodextrin electrolyte.

[0012] The third aspect of this invention provides the application of proton battery electrolyte in proton batteries.

[0013] Furthermore, the proton battery is an aqueous proton battery.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] 1. The pyrophosphate-α-cyclodextrin electrolyte provided by this invention restricts the free rotation of water molecules through strong hydrogen bonding by a large number of hydroxyl groups on the outer wall of α-cyclodextrin, reducing water activity and inhibiting water decomposition side reactions, effectively broadening the electrochemical stability window of the electrolyte. Under the conditions shown in the examples, the electrochemical stability window can reach ≥3.6 V, far exceeding that of traditional aqueous electrolytes (~1.23 V), providing a possibility for high-voltage proton batteries.

[0016] 2. The pyrophosphate-α-cyclodextrin electrolyte provided by this invention forms an ordered proton transport channel through a supramolecular hydrogen bond network, which promotes the conduction of the proton Grotthuss mechanism.

[0017] 3. The pyrophosphate-α-cyclodextrin electrolyte provided by this invention has α-CD molecules adsorbed on the electrode surface, forming a dynamic supramolecular protective layer that inhibits electrode corrosion and dissolution. Under the conditions shown in the examples, the capacity retention rate reaches 70% after 10,000 cycles at a high rate of 5 A·g⁻¹, which is attributed to the stabilizing effect of the supramolecular interface protective layer on the electrode structure. Attached Figure Description

[0018] For those skilled in the art, other related figures can be obtained from the following figures without any creative effort.

[0019] Figure 1 This is the linear sweep voltammetry curve of the proton battery electrolyte prepared in Example 1 of this invention.

[0020] Figure 2 This is the cyclic voltammetry curve of the three-electrode proton cell assembled in Embodiment 2 of the present invention.

[0021] Figure 3 This is the rate performance curve of the three-electrode proton battery assembled in Embodiment 2 of the present invention.

[0022] Figure 4 These are the constant current charge-discharge curves of the three-electrode proton battery assembled in Embodiment 2 of the present invention under different current densities.

[0023] Figure 5 The three-electrode proton battery assembled in Embodiment 2 of this invention operates at 5 A·g. -1 Long-cycle performance curves at current density. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0025] Example 1: Proton Battery Electrolyte – Pyrophosphate-α-Cyclodextrin Electrolyte

[0026] I. Composition of Pyrophosphate-α-cyclodextrin Electrolyte

[0027] The pyrophosphate-α-cyclodextrin electrolyte is prepared by mixing pyrophosphate, α-cyclodextrin, and deionized water. The molar ratio (purity ≥95 wt%) is pyrophosphate : α-cyclodextrin : deionized water = 1 : 0.0073 : 2.74.

[0028] II. Preparation Method

[0029] 1. According to the above molar ratio, add α-cyclodextrin and deionized water into a container and stir at 400 r / min until the α-cyclodextrin is completely dissolved to obtain an α-cyclodextrin aqueous solution.

[0030] 2. Place pyrophosphoric acid with a purity ≥ 95 wt% in a 50 °C water bath and preheat for 30 min to make it flowable, thus obtaining flowable pyrophosphoric acid.

[0031] 3. Slowly add the α-cyclodextrin aqueous solution obtained in step 1 to the fluid pyrophosphoric acid obtained in step 2, and mix it by ultrasonication. Cool it to room temperature to obtain the pyrophosphoric acid-α-cyclodextrin electrolyte.

[0032] III. Electrochemical Performance Testing

[0033] The prepared pyrophosphate-α-cyclodextrin electrolyte was used with titanium sheets as the working and counter electrodes, and an Ag / AgCl electrode as the reference electrode, at a scan rate of 10 mV·s. -1 The linear sweep voltammetry (LSV) curves obtained by testing in an electrolytic cell at a temperature of 25 °C are shown below. Figure 1 .

[0034] pass Figure 1 The results show that the electrochemical window of the linear sweep voltammetric curve of the pyrophosphate-α-cyclodextrin electrolyte provided by the present invention is significantly widened, and the electrochemical stability window of the proton battery electrolyte is ≥3.6 V. This indicates that the pyrophosphate-α-cyclodextrin electrolyte provided in this embodiment has a wider voltage window, which significantly alleviates the hydrogen evolution and oxygen evolution phenomena of the negative electrode material, demonstrating a significantly better effect in this regard.

[0035] Example 2: Application of pyrophosphate-α-cyclodextrin electrolyte in proton batteries

[0036] I. Assembly of Aqueous Proton Batteries

[0037] 1. Preparation of working electrode

[0038] Molybdenum trioxide, acetylene black, and polyvinylidene fluoride powder were thoroughly mixed in a mass ratio of 7:2:1 and ground for 30 minutes to obtain a positive electrode material mixture.

[0039] N-methylpyrrolidone was added to the positive electrode material mixture, stirred thoroughly, and then ground to form a mixed slurry.

[0040] Take a 2 cm × 1 cm titanium mesh and apply the mixed slurry at a concentration of 1 mg / cm using a needle scraping method. 2 -2 mg / cm 2The coating is evenly applied to the titanium mesh using a needle, and then placed in a vacuum oven and dried overnight at 60 °C-80 °C to obtain the working electrode.

[0041] 2. Preparation of the counter electrode

[0042] A counter electrode was obtained by ultrasonically cleaning a piece of carbon cloth with an area of ​​2 cm × 1 cm with water and ethanol and then vacuum drying.

[0043] 3. Battery assembly

[0044] The working electrode prepared in step 1, the counter electrode prepared in step 2, and the reference electrode being Ag / AgCl were added to the pyrophosphate-α-cyclodextrin electrolyte prepared in Example 1 to assemble an aqueous proton battery.

[0045] II. Electrochemical Testing:

[0046] The assembled aqueous proton cell was electrochemically tested within a voltage window of -0.4 V (vs. Ag / AgCl) to 0.5 V (vs. Ag / AgCl), and the results are as follows. Figures 2-5 .

[0047] Figure 2 These are the cyclic voltammograms of an assembled aqueous proton battery. From... Figure 2 It can be seen that the assembled aqueous proton battery achieves a voltage of 0.1 mV·s. -1 Up to 1 mV·s -1 Cyclic voltammetry curves at different scan rates revealed two pairs of redox peaks.

[0048] Figure 3 This is the rate performance curve of an assembled aqueous proton battery. From... Figure 3 It can be seen that at 1 A·g -1 At a current density of 201 mAh·g, the specific capacity of an aqueous proton battery can reach 201 mAh·g. -1 , in 5 A·g -1 Even at high current densities, it can still provide 171 mAh·g -1 The specific capacity, when it returns to 1 A·g -1 At a current density of [value missing], the specific capacity of the material can still be restored to 201 mAh·g. -1 The specific capacity is basically consistent with that in the initial stage. In summary, the aqueous proton battery using the pyrophosphate-α-cyclodextrin electrolyte provided by this invention achieves a specific capacity of 1 A·g -1 - 5 A·g -1 The range exhibits excellent rate capability.

[0049] Figure 4 These are the constant current charge-discharge curves of an assembled aqueous proton battery at different current densities. For example... Figure 4 As shown, as the current density increases from 1 A·g -1 Gradually increase to 5 A·g -1 The battery's discharge specific capacity is 201 mAh·g. -1 188mAh·g -1 182 mAh·g -1 176 mAh·g -1 and 171 mAh·g -1 At 1 A·g⁻¹, the discharge plateau is located at approximately 0.15 V (vs. Ag / AgCl). As the current increases to 5 A·g⁻¹, the plateau shows only slight polarization, maintaining a clear plateau characteristic. This indicates that the supramolecular electrolyte possesses excellent ion conductivity and interfacial stability, with low polarization even at high rates. These results further demonstrate that the battery exhibits excellent reaction kinetics and structural stability under different rate conditions, showcasing good potential for practical applications.

[0050] Figure 5 It is an assembled aqueous proton battery at 5 A·g -1 Long-cycle performance test curves at current density. The initial discharge capacity was 171 mAh·g⁻¹, and after 10,000 cycles, the capacity was 120 mAh·g⁻¹, with a capacity retention of 70% and an average capacity decay rate of only 0.003% per cycle. This is attributed to the dynamic protective layer formed by α-CD on the electrode surface, which effectively suppressed the dissolution and structural collapse of MoO3, while the supramolecular hydrogen bond network ensured the stability of the proton transport channels during long-term cycling.

[0051] In summary, it can be demonstrated that the modified pyrophosphate-α-cyclodextrin electrolyte exhibits superior electrochemical performance compared to other cases.

[0052] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A supramolecular proton battery electrolyte, characterized in that, The proton battery electrolyte is a pyrophosphate-α-cyclodextrin electrolyte, which is prepared by mixing pyrophosphate, α-cyclodextrin and deionized water, and a pyrophosphate-α-cyclodextrin supramolecular inclusion structure is formed in the electrolyte.

2. The supramolecular proton battery electrolyte according to claim 1, characterized in that, The molar ratio is pyrophosphate:α-cyclodextrin:deionized water = 1:(0.002 - 0.012):(2.5 - 4.0).

3. The supramolecular proton battery electrolyte according to claim 2, characterized in that, The molar ratio of pyrophosphate:α-cyclodextrin:deionized water is 1:0.0073:2.

74.

4. The supramolecular proton battery electrolyte according to claim 1, characterized in that, The purity of the pyrophosphate is ≥95 wt%.

5. The supramolecular proton battery electrolyte according to claim 1, characterized in that, The supramolecular inclusion structure is formed by the inclusion of pyrophosphate molecules in the hydrophobic cavity of α-cyclodextrin, and the hydroxyl groups on the outer wall of α-cyclodextrin form a three-dimensional hydrogen bond network with pyrophosphate and water molecules.

6. A method for preparing a supramolecular proton battery electrolyte according to any one of claims 1-5, characterized in that, The preparation method includes: mixing α-cyclodextrin with deionized water and stirring until the α-cyclodextrin is completely dissolved to obtain an α-cyclodextrin aqueous solution; preheating pyrophosphoric acid to a fluid state; slowly adding the α-cyclodextrin aqueous solution dropwise to the molten pyrophosphoric acid, stirring and ultrasonically mixing, and cooling to room temperature to obtain a pyrophosphoric acid-α-cyclodextrin electrolyte.

7. The method for preparing a supramolecular proton battery electrolyte according to claim 6, characterized in that, The preheating is carried out at 40 °C - 60 °C for 20 min - 40 min.

8. The application of the supramolecular proton battery electrolyte according to any one of claims 1-5 in a proton battery.

9. The application according to claim 8, characterized in that, The proton battery is an aqueous proton battery.

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