A pseudo-capacitance-based supercapacitor diode and a preparation method thereof

Abstract

The present application belongs to the technical field of hybrid capacitor and ion diode, and particularly relates to a pseudo-capacitance-based supercapacitor diode and a preparation method thereof. The diode of the present application comprises a pseudo-capacitance material positive electrode, a carbon material negative electrode and an aqueous alkaline electrolyte. Different from traditional semiconductor diodes and ion diodes, the novel pseudo-capacitance-based supercapacitor diode of the present application is constructed based on the ion-selective surface redox reaction of common metal oxides in an aqueous alkaline electrolyte. The device successfully integrates the one-way conduction characteristics of diodes into pseudo-capacitors, thereby realizing the functions of fast ion conduction / storage and effective blocking of unidirectional current. The pseudo-capacitance-based supercapacitor diode of the present application can be used as an energy storage unit and a computing unit with information storage function in a circuit system, and thus can be applied to ion logic circuits (AND, OR gate) and neuromorphic computing.

Description

Technical Field

[0001] This invention belongs to the field of hybrid capacitors and ion diodes, specifically relating to a pseudocapacitive supercapacitor diode and its fabrication method. Background Technology

[0002] In the family of electronic devices, a diode is a component with two electrodes exhibiting asymmetric conductance, allowing current to flow in only one direction (possessing rectification characteristics), and is a fundamental component in the development of the modern electronics industry. A semiconductor diode is constructed using the PN junction effect at the interface between P-type and N-type semiconductors, consisting of a PN junction, the semiconductor it contains, electrode leads, and a casing. The PN junction formed between the P-type and N-type semiconductors is the basic structure of solid-state electronic circuits; the unidirectional transport of electrons through the PN junction generates a rectification effect, which is the functional basis of electronic diodes, transistors, and integrated logic circuits. Ion diodes, developed based on semiconductor diodes, have attracted significant attention from researchers due to their unique ion selectivity, rectification, and switching characteristics, and are expected to be applied in novel ion-based electronic devices, such as pressure / tension sensors, signal processing, bio-functional regulation, and logic operation units. However, currently developed ion diodes still suffer from low ion conduction rates within the device. Therefore, developing ion diodes with fast ion conduction capabilities and novel rectification mechanisms will help realize their further applications in the aforementioned fields.

[0003] The concept of a supercapacitor diode (CAPode) was first proposed by Kaskel et al. in 2019. This technology integrates the characteristics of a diode into an electric double-layer capacitor, providing energy storage only in one charging direction. Subsequently, researchers constructed supercapacitor ionic diodes with tunable bias by synthesizing polyionic liquids. These two pioneering research results have provided researchers with a completely new perspective on expanding the applications of supercapacitor diodes, thereby extending supercapacitors to new application fields and enabling them to play a significant role in areas such as power grid stability, signal propagation, and logic operations. However, all of the aforementioned supercapacitor diodes have some shortcomings. For example, some studies have required strict pore-size engineering to construct CAPode devices, which significantly increases the manufacturing cost and complexity of porous carbon (especially pure microporous carbon). Other studies have successfully constructed CAPodes with forward or reverse bias charging capabilities using either polycation-based PVBIM·(TFSI)n or polyanion-based (EMIM)n·PSTFSI) as electrolytes. However, the complex synthesis process and difficulty in controlling the degree of polymerization of polyionic liquids result in higher costs compared to other electrolyte systems. Furthermore, the weak ion transport capability of ionic liquid electrolytes leads to poor fast charge-discharge performance of the devices. Therefore, developing simple, low-cost electrolyte and electrode material systems with fast ion transport, and designing novel energy storage electronic components with both energy storage and rectification characteristics, remains a significant challenge. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a pseudocapacitive supercapacitor diode. Compared with the methods of strict carbon size engineering and high-cost polyionic liquid synthesis, this invention constructs a pseudocapacitive supercapacitor diode based on the selective redox reaction of pseudocapacitive electrode materials with anions and cations in an aqueous alkaline electrolyte, thereby achieving energy storage in a single charging direction, significantly reducing device manufacturing costs, and having greater practical application value.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] This invention provides a pseudocapacitive-based supercapacitor diode, which includes a pseudocapacitive material positive electrode, a carbon material negative electrode, and an aqueous alkaline electrolyte. The pseudocapacitive material is a metal oxide that can achieve a single-ion surface redox reaction in the aqueous alkaline electrolyte.

[0007] Preferably, the pseudocapacitive material is selected from at least one of cobalt tetroxide, zinc cobaltate, hydrated tungsten trioxide, and vanadium pentoxide.

[0008] Preferably, the carbon material is selected from at least one of porous carbon, activated carbon, carbon gel, and activated carbon fiber.

[0009] Preferably, the aqueous alkaline electrolyte is selected from at least one of potassium hydroxide, sodium hydroxide, and lithium hydroxide.

[0010] Preferably, the concentration of the aqueous alkaline electrolyte is 1-6 mol / L.

[0011] Preferably, the mass ratio of the carbon material to the pseudocapacitive material is 3:1 to 10:1.

[0012] This invention also provides a method for preparing the above-mentioned pseudocapacitive supercapacitor diode, comprising the following steps:

[0013] S1. Preparation of pseudocapacitive material positive electrode and carbon material negative electrode: Disperse pseudocapacitive material or carbon material, binder and conductive additive in solvent, mix to form slurry, coat the obtained slurry onto current collector, dry and press to form electrode sheet;

[0014] S2. Assembly of pseudocapacitive supercapacitor diode: The supercapacitor diode is assembled in the order of carbon material negative electrode, separator, and pseudocapacitive material positive electrode. After adding an aqueous alkaline electrolyte, it is encapsulated to prepare the supercapacitor diode.

[0015] Preferably, the mass ratio of the pseudocapacitive material or carbon material, binder, and conductive additive is 8:1:1.

[0016] Preferably, the adhesive is selected from at least one of sodium carboxymethyl cellulose, polytetrafluoroethylene, and polyvinylidene fluoride.

[0017] Preferably, the conductive additive is selected from at least one of acetylene black, Ketjen black, carbon black, conductive graphite, and carbon nanotubes.

[0018] Preferably, the solvent is selected from at least one of water, ethanol, and N-methylpyrrolidone.

[0019] Preferably, the current collector is selected from at least one of nickel foam, carbon cloth, carbon paper, and stainless steel mesh.

[0020] Preferably, the diaphragm is selected from at least one of glass fiber, polyethylene, and polypropylene porous membranes.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] This invention discloses a pseudocapacitive-based supercapacitor diode, comprising a pseudocapacitive material positive electrode, a carbon material negative electrode, and an aqueous alkaline electrolyte. This invention utilizes an environmentally friendly, non-flammable, and low-cost aqueous alkaline electrolyte (while organic electrolytes have insurmountable drawbacks such as high cost, toxicity, and flammability / explosiveness) and common metal oxide pseudocapacitive materials (which selectively undergo selective surface redox reactions with the anions and cations in the electrolyte) to construct a novel pseudocapacitive-based supercapacitor diode.

[0023] Unlike traditional semiconductor diodes and ion diodes, the novel pseudocapacitive supercapacitor diode of this invention is constructed based on the ion-selective surface redox reaction of common metal oxides in an aqueous alkaline electrolyte. The use of an aqueous alkaline electrolyte avoids the stringent carbon electrode pore-size engineering and the complex synthesis process of polymerizing ionic liquids, and eliminates the need for a harsh anhydrous environment, thus greatly simplifying the assembly process of the supercapacitor diode and reducing costs. Furthermore, this invention uses metal oxides and carbon materials as the two electrodes to construct the pseudocapacitive supercapacitor diode, integrating the unidirectional ion transport characteristics (forward conduction, reverse cutoff) of an ion diode into the supercapacitor device. This successfully integrates the unidirectional conduction characteristic of a diode into a pseudocapacitor, achieving both rapid ion conduction / storage and effective blocking of unidirectional current. The pseudocapacitive supercapacitor diode of this invention can serve as both an energy storage unit and a computing unit with information storage capabilities in a circuit system, thus being applied in ion logic circuits ("AND" and "OR gates") and neuromorphic computing. The pseudocapacitive supercapacitor diode in this invention has not been reported domestically or internationally. It is advanced in terms of energy storage concept and rectification principle, and meets the requirements of future novel multifunctional electrochemical energy storage technologies. Attached Figure Description

[0024] Figure 1 The cyclic voltammetry curves of the zinc cobalt oxide electrode in potassium hydroxide electrolyte at different scan rates are shown.

[0025] Figure 2 The curves showing the changes in rectification ratio I and rectification ratio II of the zinc cobalt oxide electrode in potassium hydroxide electrolyte as a function of scan rate;

[0026] Figure 3 Cyclic voltammetry curves of zinc cobalt oxide-based supercapacitor diodes at different scan rates;

[0027] Figure 4 The curve showing the specific capacitance of a zinc cobalt oxide-based supercapacitor diode as a function of scan rate;

[0028] Figure 5The curve showing the change in rectification ratio II of the zinc cobalt oxide-based supercapacitor diode as a function of scan rate;

[0029] Figure 6 The curves show the capacitance retention rate and rectification ratio II of the zinc cobalt oxide-based supercapacitor diode as a function of the number of cycles.

[0030] Figure 7 Cyclic voltammetry curves of a vanadium pentoxide-based supercapacitor diode at different scan rates;

[0031] Figure 8 The cyclic voltammetry curves of a hydrated tungsten trioxide-based supercapacitor diode at different scan rates are shown. Detailed Implementation

[0032] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0034] Example 1: Fabrication of a pseudocapacitive supercapacitor diode

[0035] (1) Preparation of the positive electrode sheet: Zinc cobalt oxide (ZnCo2O4), acetylene black, and polyvinylidene fluoride (10% concentration) dissolved in N-methylpyrrolidone (NMP) were mixed in a certain mass ratio (8:1:1), and ground evenly in a mortar to obtain a stable and uniform slurry. The resulting slurry was coated onto a 1cm×1cm nickel foam substrate. After drying overnight in an oven at 80℃, the zinc cobalt oxide positive electrode sheet was obtained by pressing under a pressure of 10MPa. The loading of the positive electrode active material on the positive electrode sheet was 2.03mg / cm. 2 .

[0036] Electrochemical tests were performed on the prepared zinc cobaltate electrode. Using a conventional three-electrode system with a calomel electrode as the reference electrode and a platinum sheet as the counter electrode in 1M potassium hydroxide solution, the electrochemical performance of the zinc cobaltate electrode was tested. CV curves for different scan rates are shown below. Figure 1 As shown, a significant redox peak appears in the voltage range of 0.3–0.5V, while no significant current response is observed when the voltage window is widened to the left from 0V. From Figure 2It can be seen that the rectification ratio I (the ratio of the current value corresponding to the maximum voltage in the positive polarization region to the current value corresponding to the maximum voltage in the negative polarization region) of the zinc cobalt oxide electrode under three-electrode testing is as high as 7 to 14, which is higher than that of the current carbon-based supercapacitor diode (the rectification ratio I reported in the literature is 8, see "Adv. Mater. 2021, 2100887. Angew. Chem. 2019, 131, 13194–13199").

[0037] (2) A negative electrode sheet was prepared using commercially available YP-50F activated carbon as the negative electrode active material. The specific preparation method was as follows: YP-50F, acetylene black, and polyvinylidene fluoride dissolved in N-methylpyrrolidone (NMP) solvent were mixed in a mass ratio of 8:1:1. After being ground evenly in a mortar, a stable and uniform slurry was obtained. After being thoroughly stirred, the resulting slurry was coated onto nickel foam, dried overnight in an oven at 80℃, and then pressed into a sheet under a pressure of 10MPa to obtain the negative electrode sheet. The loading of the negative electrode active material on the negative electrode sheet was 6.01 mg / cm³. 2 (Mass of negative electrode active material YP-50F: Mass of positive electrode active material zinc cobaltate = 3:1).

[0038] (3) Place the negative electrode sheet into the 2032 type negative electrode battery case, then place the glass fiber separator and the positive electrode sheet in sequence, and inject 200μL KOH electrolyte. Then place the gasket and the positive electrode case in sequence, and finally encapsulate to make a pseudocapacitive supercapacitor diode (i.e., zinc cobalt oxide supercapacitor diode).

[0039] from Figure 3 and Figure 4 It can be seen that the supercapacitor diode exhibits a good asymmetric cyclic volt-ampere curve shape in the range of 20-200 mV / s. -1 Within the scan rate range, it exhibits almost overlapping cutoff voltage points (close to 0V) and high capacitance retention (≈70%). In practical rectification, the supercapacitor diode shows a relatively stable rectification ratio II (the ratio of the capacitance of the positive polarization region to the capacitance of the negative polarization region) at 100mV s. -1 When it is close to 0.75 (e.g.) Figure 5 (As shown). At 100mV s -1 It showed very good stability in the cyclic tests, and the capacity remained at 93% after 1000 cycles (e.g., Figure 6 As shown in the figure, the rectification ratio II increases from 0.80 to 0.82.

[0040] Example 2: Fabrication of a pseudocapacitive supercapacitor diode

[0041] The preparation method is the same as in Example 1, except that the zinc cobalt oxide material is replaced with vanadium pentoxide material.

[0042] The cyclic voltammetry curves of vanadium pentoxide-based supercapacitor diodes at different scan rates are as follows: Figure 7 As shown, the capacitance in the positive polarization region is much larger than that in the negative polarization region, and the capacitance in the negative potential region is almost negligible, indicating that the vanadium pentoxide-based supercapacitor diode has excellent rectification performance.

[0043] Example 3: Fabrication of a pseudocapacitive supercapacitor diode

[0044] The preparation method is the same as in Example 1, except that the zinc cobalt oxide material is replaced with hydrated tungsten trioxide material.

[0045] Cyclic voltammetry curves of hydrated tungsten trioxide-based supercapacitor diodes at different scan rates are shown below. Figure 8 As shown, the positive response current of the device is significantly higher than the negative response current at different scan rates. This indicates that the hydrated tungsten trioxide-based supercapacitor diode possesses excellent rectification performance.

[0046] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A pseudocapacitive-based supercapacitor diode, characterized in that, The pseudocapacitive-based supercapacitor diode includes a pseudocapacitive material positive electrode, a carbon material negative electrode, and an aqueous alkaline electrolyte; The pseudocapacitor material is selected from at least one of cobalt tetroxide, zinc cobaltate, hydrated tungsten trioxide, and vanadium pentoxide; The carbon material is selected from at least one of porous carbon, activated carbon, and carbon gel. The aqueous alkaline electrolyte is selected from at least one of potassium hydroxide, sodium hydroxide, and lithium hydroxide; The concentration of the aqueous alkaline electrolyte is 1-6 mol / L; The mass ratio of the carbon material to the pseudocapacitive material is 3:1 to 10:1; A pseudocapacitive-based supercapacitor diode is constructed by selectively redox reacting pseudocapacitive electrode materials with anions and cations in an aqueous alkaline electrolyte.

2. The method for preparing the pseudocapacitive supercapacitor diode according to claim 1, characterized in that, Includes the following steps: S1. Preparation of pseudocapacitive material positive electrode and carbon material negative electrode: Disperse pseudocapacitive material or carbon material, binder and conductive additive in solvent, mix to form slurry, coat the obtained slurry onto current collector, dry and press to form electrode sheet; S2. Assembly of pseudocapacitive supercapacitor diode: The supercapacitor diode is assembled in the order of carbon material negative electrode, separator, and pseudocapacitive material positive electrode. After adding an aqueous alkaline electrolyte, it is encapsulated to prepare the supercapacitor diode. A pseudocapacitive-based supercapacitor diode is constructed by selectively redox reacting pseudocapacitive electrode materials with anions and cations in an aqueous alkaline electrolyte.

3. The method for fabricating a pseudocapacitive supercapacitor diode according to claim 2, characterized in that, The mass ratio of the pseudocapacitive material or carbon material, binder, and conductive additive is 8:1:

1.

4. The method for preparing a pseudocapacitive supercapacitor diode according to claim 2, characterized in that, The adhesive is selected from at least one of sodium carboxymethyl cellulose, polytetrafluoroethylene, and polyvinylidene fluoride.

5. The method for fabricating a pseudocapacitive supercapacitor diode according to claim 2, characterized in that, The conductive additive is selected from at least one of acetylene black, Ketjen black, carbon black, conductive graphite, and carbon nanotubes.

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