Method for artificially constructing positive electrolyte interface layer in aqueous energy storage device

Abstract

The application belongs to the technical field of novel aqueous energy storage, and specifically discloses a method for artificially constructing a positive electrolyte interface layer in an aqueous energy storage device. The method is to first deposit a nanometer-thick positive electrolyte interface layer (CEI) on the surface of a positive electrode sheet through an atomic layer deposition process, and then use the obtained positive electrode sheet with the interface layer to build the aqueous energy storage device. The electrolyte interface construction method is simple in process, short in preparation period, and accurate and controllable in thickness of the formed interface layer. The method not only can effectively improve the interface contact problem of the electrode and the aqueous electrolyte, but also can prevent the erosion of water molecules on the electrode surface, and significantly improve the cycle stability of the positive electrode material in the aqueous electrolyte. Moreover, since the direct contact of the electrode and the electrolyte is avoided, the oxygen evolution reaction of the aqueous electrolyte can also be inhibited, thereby further expanding the working voltage window and improving the energy density of the aqueous energy storage device.

Description

Technical Field

[0001] This invention belongs to the field of novel water-based energy storage technology, and more specifically, relates to a method for artificially constructing a positive electrode electrolyte interface layer in a water-based energy storage device, which can be further combined with a flexible electrolyte to obtain a flexible water-based energy storage device. Background Technology

[0002] Currently, lithium-ion energy storage devices based on organic electrolytes are widely used in smart devices, new energy vehicles, and large power plants due to their considerable energy density. However, issues such as safety and production costs limit their large-scale application in the future. In contrast, aqueous energy storage devices have attracted much attention due to their advantages in safety, environmental protection, storage capacity, and packaging conditions. However, the thermodynamic stability voltage window of water is only 1.23V, resulting in a lower energy density for aqueous energy storage devices. Furthermore, the high activity and strong polarity of free water in aqueous electrolytes can cause dissolution of electrode materials. In addition, the unavoidable hydrogen / oxygen evolution reactions during charge and discharge also accelerate capacity decay. Therefore, improving the energy density and cycle stability of aqueous energy storage devices is a current research hotspot and challenge.

[0003] The inventors of this invention previously developed an aqueous sodium-ion hybrid capacitor and its preparation method and application (see Chinese Patent Document ZL202210539955.9). This invention uses Na3(VO)2(PO4)2F@rGO, which has high potential and energy density, as the positive electrode. By controlling the operating voltage range to 0–1.0V (vs. SCE, the same below), energy storage is achieved by utilizing only the redox peak at 0.8V, which significantly suppresses material dissolution and greatly improves cycle stability. Although dissolution is significantly suppressed, by foregoing the utilization of the redox peak at 1.2V, only 50% of the material's theoretical specific capacitance and approximately 40% of its theoretical energy density are utilized, failing to fully realize its potential as a high-voltage sodium-ion positive electrode material.

[0004] Given that the dissolution of positive electrode active materials is a common problem in current aqueous energy storage devices, if a simple and effective strategy can be adopted to solve this problem and fully utilize the energy storage potential of electrode materials, it will undoubtedly be of great significance to the promotion and application of aqueous energy storage devices. Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, the present invention aims to provide a method for artificially constructing a positive electrode electrolyte interface layer (CEI) in aqueous energy storage devices. This method utilizes atomic layer deposition (ALD) to deposit a nanoscale, uniformly thick CEI on the surface of the positive electrode sheet, thereby enhancing the electrochemical performance of the positive electrode active material in an aqueous electrolyte, particularly improving the cycle stability of the aqueous energy storage device. The CEI construction method of this invention is simple, has a short preparation cycle, and allows for precise control of the interface layer thickness. It not only effectively improves the interfacial contact between the electrode and the aqueous electrolyte but also prevents water molecules from eroding the electrode surface, significantly improving the cycle stability of the positive electrode material. Furthermore, by avoiding direct contact between the electrode and the electrolyte, it also inhibits the oxygen evolution reaction in the aqueous electrolyte, thereby further expanding the operating voltage window and increasing the energy density of the aqueous energy storage device.

[0006] To achieve the above objectives, the present invention provides a method for constructing an artificial positive electrode electrolyte interface layer in an aqueous energy storage device. The method is characterized in that the positive electrode electrolyte interface layer (CEI) with a thickness of nanometers is first deposited on the surface of the positive electrode sheet of the aqueous energy storage device by atomic layer deposition process, and then the positive electrode sheet with the interface layer deposited is used as the positive electrode to build the aqueous energy storage device.

[0007] Among them, the electrolyte of the aqueous energy storage device is water as a solvent and contains at least one of lithium salt, sodium salt, potassium salt and zinc salt.

[0008] As a further preferred embodiment of the present invention, the material of the positive electrode electrolyte interface layer is at least one selected from Al2O3, ZnO, LiF, NaF, Li3N, TiO2, and Li3PO4, preferably Al2O3.

[0009] As a further preferred embodiment of the present invention, the thickness of the positive electrode electrolyte interface layer is preferably 2-25 nm, and more preferably 20 nm.

[0010] As a further preferred embodiment of the present invention, the positive electrode sheet before the deposition of the positive electrode electrolyte interface layer is obtained by repeatedly rolling the electrode material until it is uniform and then pressing it onto the current collector, wherein the thickness of the electrode material on the current collector is 10 to 80 μm.

[0011] Preferably, both the rolling and pressing are performed using a double roller mill.

[0012] As a further preferred embodiment of the present invention, the electrode material simultaneously comprises a positive electrode active material, a conductive agent, and a binder;

[0013] Preferably, the conductive agent is conductive carbon Super P, and the binder is PTFE; in the electrode material, the mass ratio of the positive electrode active material, the conductive agent, and the binder satisfies 40-90:5-30:5-30.

[0014] As a further preferred embodiment of the present invention, the positive electrode active material is one of transition metal oxides, Prussian blue analogs, and polyanions, preferably Na3(VO)2(PO4)2F@rGO.

[0015] As a further preferred embodiment of the present invention, the positive electrode active material is Na3(VO)2(PO4)2F@rGO;

[0016] The positive electrode sheet with the deposited interface layer has also undergone electrochemical activation treatment. The voltage range used for activation is 0 to 1.5V (vs. SCE), and the activation current is 0.1 to 5C. The preferred operating voltage range is 0 to 1.5V (vs. SCE).

[0017] As a further preferred embodiment of the present invention, the current collector is one of titanium mesh, platinum mesh, and stainless steel mesh, preferably a 100-mesh titanium mesh;

[0018] Preferably, the current collector has undergone a pretreatment process, namely, it is first polished with 1000-mesh metallographic sandpaper, then sonicated in 8wt% to 30wt% hydrochloric acid for 15 minutes, and finally washed clean with ethanol.

[0019] As a further preferred embodiment of the present invention, the construction of the water-based energy storage device specifically involves assembling a negative electrode, an electrolyte, and a positive electrode, arranged in the order of negative electrode, electrolyte, and positive electrode.

[0020] As a further preferred embodiment of the present invention, the electrolyte is specifically one of a sodium-containing polyacrylamide hydrogel electrolyte, a sodium-containing polyvinyl alcohol hydrogel electrolyte, or a sodium-containing carboxymethyl cellulose sodium hydrogel electrolyte; preferably, it is a sodium-containing polyacrylamide hydrogel electrolyte.

[0021] Compared with the prior art, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0022] 1. For aqueous energy storage devices, this invention effectively solves the main problems faced by electrode materials in aqueous electrolytes by artificially depositing a nanoscale (thickness can be 1nm to 1000nm) and uniformly distributed electrolyte interface layer on the surface of the positive electrode. Specifically, it has the following three outstanding advantages: (a) It significantly alleviates the dissolution of active materials and improves the cycle performance of the positive electrode. Taking the embodiments of this invention below as an example, after depositing 20nm of Al2O3 on the surface, the cycle performance of the Na3(VO)2(PO4)2F@rGO positive electrode in 17m NaClO4 electrolyte is improved by more than 2 times. (b) It suppresses the oxygen evolution reaction during the charging and discharging process and improves the coulombic efficiency. Taking the embodiments of this invention below as an example, after depositing 20nm of Al2O3 on the electrode surface, the initial coulombic efficiency is increased from 54.32% to 67.71%, and the number of bubbles adsorbed on the positive electrode surface is also significantly reduced (the oxygen evolution reaction will produce oxygen, and the gas production will accelerate the dissolution and shedding of active materials, affecting the cycle performance; in severe cases, it will also cause device bulging and create safety hazards). (c) Due to the electronic insulating properties of the interface layer, the self-discharge time of the device can be extended to a certain extent.

[0023] The cathode electrolyte interphase (CEI) plays a crucial role in protecting battery electrodes and is a prerequisite for the long-term cycling and commercial application of lithium / sodium-ion organic batteries (with organic electrolytes). As a passivation layer on the cathode surface, the CEI allows ions to pass freely but blocks electron transport, effectively preventing direct contact between the electrolyte and the electrode to improve cycle stability. The formation of the CEI originates from the oxidative decomposition of the electrolyte, with ionic compounds generated during the reaction being its main component. However, for aqueous energy storage devices, due to the high polarity of water, the ionic compounds generated by the oxidative decomposition of the electrolyte have high solubility in aqueous electrolytes and are difficult to maintain stably. Because the cathode lacks CEI protection during long cycles, a series of side reactions continuously occur at the electrode-electrolyte interface, including material structure collapse and dissolution, oxygen evolution reaction, and other irreversible capacity decay processes, leading to a sharp deterioration in electrode performance.

[0024] Current research often employs the strategy of adding organic additives to aqueous electrolytes. While this can adjust the solvation structure and form a stable CEI in situ on the electrode surface, it is difficult to control the thickness and uniformity of the CEI, and it also reduces the conductivity of the electrolyte, both of which affect the rate performance and power density of the device. This invention, however, eliminates the need for organic additives to adjust the aqueous electrolyte. It uses atomic layer deposition (ALD) to deposit a nanoscale CEI layer with uniform thickness on the surface of the positive electrode. This allows for precise control of the interface layer thickness and good uniformity by adjusting the number of cycles during ALD operation. Furthermore, the ALD process allows for more flexible selection and control of the CEI composition, resulting in good versatility.

[0025] 2. Taking Na3(VO)2(PO4)2F@rGO, modified with graphene composite, as the positive electrode active material for an aqueous energy storage device as an example, its high theoretical energy density (500Wh kg-1) and operating voltage plateau (0.8 / 1.2V vs. SCE) make it an ideal positive electrode material for sodium storage, significantly improving the device's operating voltage and endurance. Based on the Na3(VO)2(PO4)2F@rGO positive electrode sheet with an interface layer obtained by the method of this invention, the voltage range used for electrochemical activation is 0–1.5V (vs. SCE), and the activation current is 0.1–5C (1C = 130mAh g). -1 To form a stable ion diffusion channel; the working voltage range is selected according to the working voltage range of the paired negative electrode, and is particularly preferably 0 to 1.5V (vs. SCE), which can bring out the potential of the material as a high-voltage sodium ion positive electrode material. Compared with the authorized patent (i.e., Chinese patent document ZL202210539955.9), the working voltage can be increased by 0.2V, the specific capacity can be increased by 1 time, and the energy density can be increased by 1.5 times.

[0026] 3. In particular, this invention can use Al2O3 as the positive electrode electrolyte interface layer material. Taking the use of graphene-modified Na3(VO)2(PO4)2F@rGO as the positive electrode active material in aqueous energy storage devices as an example, Al2O3 can not only form stable ion diffusion channels during electrochemical activation, but also form new ionic compounds through in-situ reactions, improving the ion diffusion capacity and chemical stability of the interface layer. The chemical reaction formula includes, for example:

[0027] Al₂O₃ + 6F - +3H₂O→AlF₃+6OH⁻ -

[0028] The above-mentioned conversion reaction only occurs in aqueous electrolytes. Taking an aqueous electrolyte containing sodium salts as an example, since F - A stronger electrostatic attraction to positive charges can promote Na + The diffusion rate in the interface layer; in addition, AlF3 has good chemical stability and can slow down the erosion of the interface layer by the electrolyte.

[0029] Taking the following embodiments as an example, the present invention preferably controls the thickness of CEI to 20nm, which has the best rate performance.

[0030] 4. Based on this invention, taking a 17m NaClO4 electrolyte as an example (other high-concentration salt-in-water electrolytes can also be used), numerous studies have shown that high-concentration salt-in-water electrolytes can alter the solvation structure and broaden the voltage window of the electrolyte, thereby leveraging the advantages of high-voltage electrodes. Taking the embodiments described later in this invention as examples, the stable electrochemical window of the 17m NaClO4 electrolyte is 2.6V, with 1.5V in the positive electrode direction, which can meet the requirements of all positive electrode materials, including Na3(VO)2(PO4)2F@rGO. Furthermore, because the electrolyte has a low free water content and high viscosity, it can suppress ion diffusion from a kinetic perspective, and also greatly alleviate the dissolution problem of the electrolyte material.

[0031] 5. Based on this invention, taking the use of ZTC as the negative electrode of an energy storage device as an example, this material has a high efficiency of up to 3200 m... 2 g -1 With its high specific surface area and well-developed hierarchical pore structure, the energy storage mechanism of ZTC mainly manifests as pseudocapacitive behavior resulting from redox reactions of abundant oxygen-containing functional groups on the surface. Therefore, when ZTC is used as the negative electrode active material, the device falls into the category of aqueous hybrid capacitors. Given ZTC's extremely high specific capacitance and excellent rate performance, taking the embodiments described later as examples, ZTC at 0.5 A g... -1 It exhibits a high current density of up to 110 mAh g -1 The pseudocapacitance, even at 20A g -1 When used, it exhibits approximately 63% capacity retention, which is far superior to the electrochemical performance of commercial activated carbon. Therefore, using ZTC as the negative electrode active material can further improve the energy density and power density of the device.

[0032] Taking the following embodiments as examples, the typical representative of water-based energy storage devices obtained based on the present invention—the water-based sodium-ion hybrid capacitor—uses the polyanionic material Na3(VO)2(PO4)2F@rGO as the positive electrode, which has ultrafast ion transport characteristics and excellent rate performance. It uses ZTC, which has an ultra-large specific surface area, as the negative electrode. After simple activation treatment, it exhibits a capacity of 110 mAh g / g. -1 The specific capacity (at a current density of 0.5 A / g) can effectively solve the problems of insufficient rate performance, poor cycle performance, severe self-discharge, and limited application scenarios caused by the easy dissolution of electrode materials in aqueous electrolytes.

[0033] 6. Furthermore, consistent with existing technologies, by introducing a cross-linked network, especially polyacrylamide (or polyvinyl alcohol, sodium carboxymethyl cellulose), into the electrolyte, hydrogel electrolytes with flexibility and excellent mechanical properties can be prepared. The corresponding energy storage device will be a flexible device, particularly suitable for wearable electronic devices. The aqueous energy storage device obtained based on this invention can, for example, use a polyacrylamide-based hydrogel electrolyte, which not only further improves the device's cycle performance but also results in a flexible aqueous energy storage device, particularly applicable to the field of wearable smart electronic products. Taking the use of a polyacrylamide-based hydrogel electrolyte as an example, by utilizing the "confining effect" of the gel electrolyte (polyacrylamide can also be replaced by polyvinyl alcohol or sodium carboxymethyl cellulose), the high-concentration salt-encapsulated water electrolyte synergistically inhibits the dissolution of the positive electrode material, further improving the device's cycle life and imparting flexibility, without significant negative impact on the negative electrode, making it particularly suitable for wearable electronic products. As shown in the embodiments described later in this invention, after 1000 cycles, the capacity retention rate of the flexible device remains as high as 77.0%. Attached Figure Description

[0034] Figure 1 The image shows a transmission electron microscope (TEM) image of the surface after a 20 nm Al2O3 electrolyte interface layer was deposited in Example 1 (corresponding to sample ALD-150). In the image, NVOPF@rGO is Na3(VO)2(PO4)2F@rGO.

[0035] Figure 2 The figure shows the rate performance of Na3(VO)2(PO4)2F@rGO positive electrode sheets with Al2O3 electrolyte interface layers of different thicknesses deposited on the surface in Example 1 (corresponding to deposition cycle numbers of 50, 150 and 250, respectively). The figure shows the rate performance at current densities of 1C, 2C, 5C, 10C, 20C, 50C and 100C.

[0036] Figure 3 The cycling performance and first-cycle coulombic efficiency of the Na3(VO)2(PO4)2F@rGO positive electrode sheets with Al2O3 electrolyte interface layers of different thicknesses deposited on their surfaces are compared in Example 1. Figure 3 (a) in the figure corresponds to the cycle performance (under 1C conditions). Figure 3 (b) in the equation corresponds to the Coulomb efficiency in the first round.

[0037] Figure 4 The interfacial performance of the Na3(VO)2(PO4)2F@rGO positive electrode sheet with a 20nm Al2O3 electrolyte interface layer deposited on its surface is characterized; among them, Figure 4 (a) in the image corresponds to the optical photograph of the contact angle test. Figure 4 (b) in the image corresponds to an optical photograph taken after 100 cycles at a current density of 1C.

[0038] Figure 5 This is the rate performance of the activated ZTC anode in Example 1. The figure shows the rate performance at 0.5 Ag. -1 1Ag -1 2Ag -1 5Ag -1 10Ag -1 15Ag -1 20Ag -1 Rate performance under certain conditions.

[0039] Figure 6 This is the CV curve of the flexible aqueous sodium ion hybrid capacitor in Example 1 at different scan rates.

[0040] Figure 7 This is the rate performance of the flexible aqueous sodium ion hybrid capacitor in Example 1. The figure shows the rate performance at 0.2 Ag. -1 0.5Ag -1 1Ag -1 2Ag -1 5Ag -1 10Ag -1 Rate performance under certain conditions.

[0041] Figure 8 The cycling performance (1Ag) of the flexible aqueous sodium ion hybrid capacitor in Example 1 is shown. -1 conditions).

[0042] Figure 9 This demonstrates the performance of the flexible aqueous sodium ion hybrid capacitor in Example 1 in resisting environmental changes; among which, Figure 9 (a) in the graph shows the change in volume with temperature. Figure 9 (b) in the figure shows the change of capacity with pressure.

[0043] Figure 10 The cycling performance of the Na3(VO)2(PO4)2F@rGO positive electrode in Comparative Example 1 is shown when no electrolyte interface layer is deposited on the surface (100 cycles at 1C current density).

[0044] Figure 11 This describes the interfacial performance of the Na3(VO)2(PO4)2F@rGO positive electrode sheet without a deposited electrolyte interface layer on its surface; among which... Figure 11 (a) in the image corresponds to the optical photograph of the contact angle test. Figure 11 (b) in the image corresponds to an optical photograph taken after 100 cycles at a current density of 1C.

[0045] Figure 12The cycling performance (1Ag) of the hybrid capacitor with 17m NaClO4 liquid electrolyte in Example 3 is shown. -1 conditions).

[0046] Figure 13 This is a schematic diagram of the fabrication process of a positive electrode sheet with an interface layer deposited on its surface, as described in an embodiment of the present invention. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0048] To address the issues of easy dissolution and poor cycle stability of electrode materials in aqueous electrolytes, this invention proposes a method for constructing an artificial positive electrode electrolyte interface. By artificially depositing a nanoscale and uniformly distributed electrolyte interface layer on the surface of the positive electrode sheet, the resulting positive electrode sheet with the deposited interface layer can be used as the positive electrode to build an aqueous energy storage device.

[0049] like Figure 13 As shown, the positive electrode sheet can be obtained by repeatedly rolling the electrode material into a uniform shape using a roller mill and then pressing it onto the current collector. The thickness of the electrode material can be 10–80 μm. It is then dried in a vacuum drying oven. Finally, an atomic layer deposition process is used to construct a nanoscale electrolyte interface layer with uniform thickness on the surface of the positive electrode sheet.

[0050] The positive electrode sheet with the deposited interface layer obtained by the above method for constructing an artificial positive electrode electrolyte interface layer can be used as a positive electrode to build an aqueous energy storage device, for example, it may include the following steps:

[0051] (1) Activation of the positive electrode: A three-electrode system was adopted, with the positive electrode plate with the interface layer deposited as the working electrode, the Pt plate as the counter electrode, and the calomel electrode as the reference electrode, and the electrode pressure was set to 0.02–0.2 A g. -1 The current density is cycled 1 to 5 times to activate the electrode, with a voltage range of 0 to 1.5V (vs. SCE);

[0052] (2) The electrolyte is prepared by using water as a solvent and containing at least one of lithium salt, sodium salt, potassium salt and zinc salt, preferably sodium salt.

[0053] (3) Preparation of negative electrode sheet: First, the negative electrode active material, conductive carbon SP and binder PTFE are mixed evenly in a mortar and then rolled into a sheet. The mass ratio of the three is 40-90:5-30:5-30. Then, the sheet is pressed onto a pretreated titanium mesh by a tablet press with a pressure of 5-20 kPa. The negative electrode active material is either a (pseudo)capacitive material or a battery material, preferably a pseudocapacitive carbon-based material zeolite template carbon (ZTC). ZTC needs to be activated. For the specific process flow, please refer to the Chinese patent "A Flexible Aqueous Sodium Ion Mixed Capacitor and Its Preparation Method and Application", patent number: CN202210539955.9. The pretreatment process is mainly to remove oxides and impurities on the surface. The roughness can be increased by polishing and other processes to strengthen the bonding force between the electrode material and the current collector. Specifically, it can be polished with 1000-mesh metallographic sandpaper, then placed in hydrochloric acid with a mass fraction of 8%-30% and sonicated for 15 minutes, and finally washed with ethanol.

[0054] (4) Construction of the aqueous energy storage device: Assemble the negative electrode, electrolyte, and positive electrode in sequence to obtain the aqueous energy storage device. Before assembly, the positive and negative electrodes should be capacity-matched. Taking Na3(VO)2(PO4)2F@rGO as the positive electrode active material and ZTC as the negative electrode active material as an example, the mass ratio of active materials in the positive and negative electrode sheets is 1:0.6~1.3. According to the preferred conditions, the constructed aqueous energy storage device belongs to the category of hybrid capacitors.

[0055] Taking sodium salt as an example of the electrolyte in an aqueous energy storage device, the electrolyte can be, for example, one of the following flexible electrolytes: sodium-containing polyacrylamide hydrogel electrolyte, sodium-containing polyvinyl alcohol hydrogel electrolyte, or sodium-containing carboxymethyl cellulose sodium hydrogel electrolyte, thereby obtaining a flexible energy storage device (i.e., a flexible aqueous sodium ion hybrid capacitor); taking sodium-containing polyacrylamide hydrogel electrolyte as an example, it can be prepared according to existing technology, and step (2) may include the following sub-steps:

[0056] (2-1) Prepare an aqueous solution of sodium salt, wherein the sodium salt is at least one of sodium perchlorate, sodium chloride, sodium acetate, sodium nitrate, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide;

[0057] (2-2) Preparation of gel precursor solution: Under stirring conditions, monomer, crosslinking agent and initiator are added to the aqueous solution of sodium salt in sequence and stirred for 2-30 min. After being sonicated for 5-30 min and vacuum defoamed for 5-20 min, the gel precursor solution is obtained.

[0058] Wherein, the monomer is acrylamide, the crosslinking agent is N,N'-methylenebisacrylamide, and the initiator is potassium persulfate (or sodium persulfate); preferably, the amounts of monomer, crosslinking agent, and initiator added are: per 10 mL of sodium salt aqueous solution, the amount of monomer added is 0.5-1.5 g, the amount of crosslinking agent added is 1-10 mg, and the amount of initiator added is 2-15 mg;

[0059] (2-3) The curing of the gel precursor solution is preferably carried out at a constant temperature of 25-80°C for 2-24 hours to obtain a sodium salt-containing polyacrylamide hydrogel electrolyte.

[0060] For a detailed example, a flexible water-based energy storage device can be fabricated according to the following steps:

[0061] (I) Preparation and activation of positive electrode sheet

[0062] (1) The positive electrode active material, conductive carbon Super P and binder PTFE with a mass ratio of 40-90:5-30:5-30 are ground into a ball in a quartz mortar; then the electrode material is repeatedly rolled and pressed evenly by a roller mill and pressed onto the pretreated current collector, and then dried in a vacuum drying oven. The thickness of the electrode material is controlled to be 10-80 μm.

[0063] (2) An electrolyte interface layer of nanoscale and uniform thickness is constructed on the surface of the above-mentioned positive electrode using atomic layer deposition (ALD). The interface layer is at least one of Al2O3, ZnO, LiF, NaF, Li3N, TiO2, and Li3PO4. The thickness of the interface layer is controlled between 2 and 25 nm by controlling the operating parameters of the ALD equipment.

[0064] (3) The positive electrode with an artificial electrolyte interface layer on its surface needs to be activated. The activation process is as follows: a three-electrode system is used, with the positive electrode plate with the interface layer deposited as the working electrode, the Pt plate as the counter electrode, and the calomel electrode as the reference electrode, and the electrode is set to 0.02~0.2A g. -1 The current density is cycled 1 to 5 times to activate the electrode, with a voltage range of 0 to 1.5V (vs. SCE).

[0065] (II) Preparation and activation of negative electrode sheet

[0066] The negative electrode active material, conductive carbon Super P, and binder PTFE are ground evenly in a quartz mortar at a mass ratio of 40-90:5-30:5-30. After 10-40 minutes, a uniform and shiny electrode sheet is formed. Then, it is pressed onto the current collector using a tablet press with a pressure of 5-20 kPa. Finally, it is placed in a vacuum drying oven at 40-100℃ for 10-24 hours. Alternatively, step (1) in the preparation and activation of the positive electrode sheet can be used to prepare the negative electrode sheet.

[0067] (III) Preparation of Polyacrylamide Hydrogel Electrolytes

[0068] (1) Prepare a high-concentration salt-in-water electrolyte, wherein the solute in the electrolyte is at least one of lithium salt, sodium salt, potassium salt, and zinc salt. For example, the concentration of LiTSFI electrolyte is 21 mg, and the concentration of NaClO4 electrolyte is 17 mg.

[0069] (2) Preparation of the gel precursor solution. Under stirring conditions, monomer (acrylamide), crosslinking agent (N,N'-methylenebisacrylamide), and initiator (potassium persulfate or sodium persulfate) are added sequentially. The mixture is stirred for 2–30 min and then defoamed under vacuum for 10–50 min to obtain the gel precursor solution. Specifically, for every 10 mL of sodium salt solution, the monomer addition is 0.5–1.5 g, the crosslinking agent addition is 1–10 mg, and the initiator addition is 2–15 mg.

[0070] (3) Curing of the gel precursor solution. The curing conditions are 25-80℃, and the temperature is maintained for 2-24 hours.

[0071] If polyvinyl alcohol gel electrolyte or sodium carboxymethyl cellulose gel electrolyte is used instead of polyacrylamide gel electrolyte, then step (iii) is based on the high concentration of salt-encapsulated water electrolyte obtained in step (1), heating the aqueous solution of sodium salt to 40-90°C, adding a certain amount of polyvinyl alcohol or sodium carboxymethyl cellulose raw material while stirring, and obtaining the gel precursor solution after complete dissolution; allowing it to stand and cool, and obtaining the gel electrolyte after cooling to room temperature.

[0072] (iv) Construction of flexible aqueous sodium ion hybrid capacitor

[0073] (1) First, the positive and negative electrodes are matched in capacity. The mass ratio of active materials in the positive and negative electrode plates is controlled to be 1:0.6 to 1.3.

[0074] (2) A flexible aqueous energy storage device can be obtained by assembling the negative electrode, gel electrolyte, and positive electrode in sequence. Alternatively, the positive and negative electrode sheets can be fixed in a mold first, and a precursor liquid can be injected into the mold and then cured under the above curing conditions to obtain an integrated flexible hybrid capacitor.

[0075] The following are specific examples:

[0076] Example 1

[0077] In this example, Na3(VO)2(PO4)2F@rGO is used as the positive electrode active material, Al2O3 is deposited on the surface as the electrolyte interface layer, ZTC is used as the negative electrode active material, and PAM-17m NaClO4 gel is used as the electrolyte. The flexible water-based energy storage device constructed belongs to the category of sodium-ion hybrid capacitors.

[0078] (I) Preparation of Na3(VO)2(PO4)2F@rGO electrode

[0079] (1) Take 359mg C 15 H 21 O6V, 104 μL of 85 wt% H3PO4, and 71.5 mg of NaF were dissolved in a mixed solution of 3 mL ethanol and 1 mL acetone. Next, 4.5 g of 1 wt% graphene oxide aqueous solution was added to the mixed solution, and after uniform dispersion, the solution was transferred to a 25 mL PTFE reactor. The reaction was carried out at 120 °C for 10 h in a constant temperature drying oven for a solvothermal reaction. After the reaction, the product was washed three times with ethanol and deionized water, and dried to obtain Na3(VO)2(PO4)2F@rGO powder.

[0080] (2) Grind Na3(VO)2(PO4)2F@rGO, conductive carbon Super P and binder PTFE in a quartz mortar with a mass ratio of 40~90:5~30:5~30 into a ball; then press the above electrode material repeatedly and evenly with a roller mill and press it onto the pretreated current collector, and dry it in a vacuum drying oven. The thickness of the electrode material is controlled to be 50μm.

[0081] (3) An Al2O3 layer is constructed on the surface of the above positive electrode as an electrolyte interface layer using atomic layer deposition technology. In this embodiment, the NCE-200R model equipment produced by Dongguan Nafeng Microelectronics Equipment Co., Ltd. is used. Under vacuum conditions, by setting the temperature of the reaction chamber to 180-200℃, a certain amount of Al source precursor material trimethylaluminum is sprayed into the reaction chamber in each deposition process. A dense Al2O3 interface layer is generated through the reaction of trimethylaluminum with water and ozone. The methyl groups are discharged from the reaction system in the form of methane. By controlling the number of deposition cycles, the thickness of the interface layer can be precisely controlled.

[0082] In this embodiment, the deposition cycle numbers were controlled to be 50, 150, and 250 cycles, respectively, to obtain samples of different thicknesses (denoted as ALD-50, ALD-150, and ALD-250, respectively). Characterization by transmission electron microscopy showed that the thickness of the interface layer on the surface of the ALD-150 sample was approximately 20 nm (e.g., ...). Figure 1 (as shown);

[0083] (4) Using the positive electrode obtained in step (3) as the working electrode, the Pt electrode as the counter electrode, and the calomel electrode as the reference electrode, set the electrode to 0.02A g. -1The current density was adjusted, and the electrode was activated by two charge-discharge cycles within a voltage range of 0.2–1.2 V (vs. SCE). After activation, the electrode was placed in a 17 mL NaClO4 solution for later use as the positive electrode of a hybrid capacitor. The rate performance of samples ALD-50, ALD-150, and ALD-250 is as follows: Figure 2 As shown, the cycle performance and the corresponding first-cycle coulomb efficiency are as follows: Figure 3 As shown. Among them, the ALD-150 sample has the best overall performance and is the optimal choice, which is used to construct energy storage devices (subsequent examples also use the same setting of 150 ALD deposition cycles, resulting in an interface layer with a thickness of 20 nm).

[0084] (II) Preparation of ZTC Electrode

[0085] (1) NaY type zeolite molecular sieve was immersed in furfuryl alcohol solution for 1 h, propylene was vapor-deposited at 750 °C, and then heat-treated at 900 °C for 3 h under argon atmosphere to enhance structural strength; then the zeolite molecular sieve template was dissolved with HF at room temperature; finally, ZTC was obtained by vacuum degassing at 200 °C for 24 h.

[0086] (2) ZTC, conductive carbon Super P and binder PTFE were ground evenly in a quartz mortar at a mass ratio of 50:25:25. After 40 minutes, a uniform and shiny electrode sheet was formed. Then, the electrode sheet was pressed onto a 100-mesh Ti mesh using a tablet press at a pressure of 12 MPa. Finally, it was placed in a vacuum drying oven at 40°C for 24 hours to obtain the ZTC electrode.

[0087] (3) Using a ZTC electrode as the working electrode, a Pt sheet as the counter electrode, and calomel as the reference electrode, a three-electrode system was employed. The electrode was activated by cyclic scanning five times in a 17 mL NaClO4 solution at a scan rate of 10 mV / s within a voltage range of -0.6 to 1.4 V. The electrode sheet was then placed in a 17 mL NaClO4 solution for later use as the negative electrode of a hybrid capacitor. Its rate performance is as follows: Figure 5 As shown.

[0088] (III) Fabrication of 17m NaClO4-PAM-based integrated hybrid capacitor

[0089] (1) Measure 10 mL of deionized water, heat it in a water bath to 40 °C, and add 20.81 g of NaClO4 while stirring. After it is completely dissolved, set it aside for use.

[0090] (2) Add 1g acrylamide, 5mg N,N'-methylenebisacrylamide and 10mg potassium persulfate under stirring conditions; continue stirring for 20min and vacuum defoaming for 10min to obtain gel precursor solution.

[0091] (3) The mass ratio of active materials in the positive and negative electrode sheets is controlled to 1:0.8 and fixed in the mold. The mold used in this embodiment is a self-made mold with a sandwich structure of "glass slide-rubber sheet-glass slide". The outer dimensions of the rubber sheet are the same as the size of the glass slide, and the middle is hollowed out for the injection of the gel precursor (of course, other shapes of molds can also be used according to actual needs).

[0092] (4) Inject the above-mentioned precursor liquid into the mold and polymerize it in situ in a constant temperature oven at 60°C for 4 hours to obtain an integrated flexible hybrid capacitor.

[0093] The obtained device was subjected to electrochemical performance testing. The test results showed that the flexible aqueous sodium-ion hybrid capacitor could provide a voltage of 2.3V and had excellent rate performance. The CV curves at different scan rates are shown in the figure. Figure 6 For rate performance, see Figure 7 ,from Figure 7 It can be known that at 0.2Ag -1 At a current density of [value missing], the device can provide 40 mAh g [value missing]. -1 It has a specific capacity of around 1A g and good cycling performance. -1 At the specified current density, after 1000 cycles, the capacity retention was 77.0%. Figure 8 As shown, compared to the device using liquid electrolyte in Comparative Example 1 described later, the cycle performance is improved by more than 2 times. Based on this Example 1, the resistance to environmental changes of the paired flexible device is demonstrated, as follows: Figure 9 As shown.

[0094] Example 2

[0095] In this example, Na3(VO)2(PO4)2F@rGO is used as the positive electrode active material, Al2O3 is deposited on the surface as the electrolyte interface layer, ZTC is used as the negative electrode active material, and PAM-21m LiTSFI gel is used as the electrolyte. The flexible aqueous energy storage device constructed belongs to the category of lithium-ion hybrid capacitors.

[0096] (I) Preparation of Na3(VO)2(PO4)2F@rGO electrode

[0097] (1) Take 359mg C 15 H 21O6V, 104 μL of 85 wt% H3PO4, and 71.5 mg of NaF were dissolved in a mixed solution of 3 mL ethanol and 1 mL acetone. Next, 4.5 g of 1 wt% graphene oxide aqueous solution was added to the mixed solution, and after uniform dispersion, the solution was transferred to a 25 mL PTFE reactor. The reaction was carried out at 120 °C for 10 h in a constant temperature drying oven for a solvothermal reaction. After the reaction, the product was washed three times with ethanol and deionized water, and dried to obtain Na3(VO)2(PO4)2F@rGO powder.

[0098] (2) Grind Na3(VO)2(PO4)2F@rGO, conductive carbon Super P and binder PTFE in a quartz mortar with a mass ratio of 40~90:5~30:5~30 into a ball; then press the above electrode material repeatedly and evenly with a roller mill and press it onto the pretreated current collector, and dry it in a vacuum drying oven. The thickness of the electrode material is controlled to be 50μm.

[0099] (3) An Al2O3 layer is constructed on the surface of the above positive electrode as an electrolyte interface layer using atomic layer deposition technology, and the thickness of the interface layer is controlled at 20 nm.

[0100] (4) Using the positive electrode obtained in step (3) as the working electrode, the Pt electrode as the counter electrode, and the calomel electrode as the reference electrode, set the electrode to 0.02A g. -1 The electrode was activated by two charge-discharge cycles at a current density of 0.2–1.2 V (vs. SCE). After activation, the electrode was placed in 21 mL of LiTSFI solution for later use as the positive electrode of a hybrid capacitor.

[0101] (II) Preparation of ZTC Electrode

[0102] (1) NaY type zeolite molecular sieve was immersed in furfuryl alcohol solution for 1 h, propylene was vapor-deposited at 750 °C, and then heat-treated at 900 °C for 3 h under argon atmosphere to enhance structural strength; then the zeolite molecular sieve template was dissolved with HF at room temperature; finally, ZTC was obtained by vacuum degassing at 200 °C for 24 h.

[0103] (2) ZTC, conductive carbon Super P and binder PTFE were ground evenly in a quartz mortar at a mass ratio of 50:25:25. After 40 minutes, a uniform and shiny electrode sheet was formed. Then, the electrode sheet was pressed onto a 100-mesh Ti mesh using a tablet press at a pressure of 12 MPa. Finally, it was placed in a vacuum drying oven at 40°C for 24 hours to obtain the ZTC electrode.

[0104] (3) Using a ZTC electrode as the working electrode, a Pt sheet as the counter electrode, and calomel as the reference electrode, a three-electrode system was employed. The electrode was activated by cyclically scanning for 5 cycles in a 21 mL LiTSFI solution at a scan rate of 10 mV / s within a voltage range of -0.6 to 1.4 V. The electrode sheet was then placed in a 21 mL LiTSFI solution for later use as the negative electrode of a hybrid capacitor.

[0105] (III) Fabrication of 21m LiTSFI-PAM-based integrated hybrid capacitor

[0106] (1) Measure 10 mL of deionized water, heat it in a water bath to 40 °C, and add 60.27 g of LiTSFI while stirring. After it is completely dissolved, set it aside for use.

[0107] (2) Add 1g acrylamide, 5mg N,N'-methylenebisacrylamide and 10mg potassium persulfate under stirring conditions; continue stirring for 20min and vacuum defoaming for 10min to obtain gel precursor solution.

[0108] (3) The mass ratio of active materials in the positive and negative electrode sheets is controlled to 1:0.8 and fixed in a self-made mold.

[0109] (4) Inject the above-mentioned precursor liquid into the mold and polymerize it in situ in a constant temperature oven at 60°C for 4 hours to obtain an integrated flexible hybrid capacitor.

[0110] Of course, in addition to gel electrolytes, this invention is also applicable to liquid electrolytes, such as:

[0111] Example 3

[0112] In this embodiment, Na3(VO)2(PO4)2F@rGO is used as the positive electrode active material, Al2O3 is deposited on the surface as the electrolyte interface layer, ZTC is used as the negative electrode active material, and 17m NaClO4 is used as the electrolyte.

[0113] (I) Preparation of Na3(VO)2(PO4)2F@rGO electrode

[0114] (1) Take 359mg C 15 H 21 O6V, 104 μL of 85 wt% H3PO4, and 71.5 mg of NaF were dissolved in a mixed solution of 3 mL ethanol and 1 mL acetone. Next, 4.5 g of 1 wt% graphene oxide aqueous solution was added to the mixed solution, and after uniform dispersion, the solution was transferred to a 25 mL PTFE reactor. The reaction was carried out at 120 °C for 10 h in a constant temperature drying oven for a solvothermal reaction. After the reaction, the product was washed three times with ethanol and deionized water, and dried to obtain Na3(VO)2(PO4)2F@rGO powder.

[0115] (2) Grind Na3(VO)2(PO4)2F@rGO, conductive carbon Super P and binder PTFE in a quartz mortar with a mass ratio of 40~90:5~30:5~30 into a ball; then press the above electrode material repeatedly and evenly with a roller mill and press it onto the pretreated current collector, and dry it in a vacuum drying oven. The thickness of the electrode material is controlled to be 50μm.

[0116] (3) An Al2O3 layer is constructed on the surface of the above positive electrode as an electrolyte interface layer using atomic layer deposition technology, and the thickness of the interface layer is controlled at 20 nm.

[0117] (4) Using the positive electrode obtained in step (3) as the working electrode, the Pt electrode as the counter electrode, and the calomel electrode as the reference electrode, set the electrode to 0.02A g. -1 The electrode was activated by cycling through two current densities and performing a charge-discharge cycle, with a voltage range of 0.2–1.2 V (vs. SCE). After activation, the electrode was placed in a 17 mL NaClO4 solution for later use as the positive electrode of a hybrid capacitor.

[0118] (II) Preparation of ZTC Electrode

[0119] (1) NaY type zeolite molecular sieve was immersed in furfuryl alcohol solution for 1 h, propylene was vapor-deposited at 750 °C, and then heat-treated at 900 °C for 3 h under argon atmosphere to enhance structural strength; then the zeolite molecular sieve template was dissolved with HF at room temperature; finally, ZTC was obtained by vacuum degassing at 200 °C for 24 h.

[0120] (2) ZTC, conductive carbon Super P and binder PTFE were ground evenly in a quartz mortar at a mass ratio of 50:25:25. After 40 minutes, a uniform and shiny electrode sheet was formed. Then, the electrode sheet was pressed onto a 100-mesh Ti mesh using a tablet press at a pressure of 12 MPa. Finally, it was placed in a vacuum drying oven at 40°C for 24 hours to obtain the ZTC electrode.

[0121] (3) Using the ZTC electrode as the working electrode, the Pt sheet as the counter electrode, and the calomel electrode as the reference electrode, a three-electrode system was adopted. The electrode was activated by cyclically scanning for 5 cycles in a 17 mL NaClO4 solution at a scan rate of 10 mV / s within a voltage range of -0.6 to 1.4 V. The electrode sheet was then placed in a 17 mL NaClO4 solution for later use as the negative electrode of a hybrid capacitor.

[0122] (III) Preparation of 17m NaClO4 mixed capacitor

[0123] A button cell was assembled sequentially with the positive electrode, a commercially available separator (with an appropriate amount of 17m NaClO4 added), and the negative electrode, and the electrochemical performance of the resulting device was tested. The test results show that this aqueous sodium-ion hybrid capacitor can provide a voltage of 2.3V, exhibiting excellent rate performance. Its cycle performance was also measured. Figure 12 As shown.

[0124] Comparative Example 1

[0125] In this comparative example, Na3(VO)2(PO4)2F@rGO was used as the positive electrode active material, ZTC as the negative electrode active material, and PAM-17m NaClO4 gel as the electrolyte. No artificial interface layer was constructed on the surface of the positive electrode sheet.

[0126] (I) Preparation of Na3(VO)2(PO4)2F@rGO electrode

[0127] (1) Take 359mg C 15 H 21 O6V, 104 μL of 85 wt% H3PO4, and 71.5 mg of NaF were dissolved in a mixed solution of 3 mL ethanol and 1 mL acetone. Next, 4.5 g of 1 wt% graphene oxide aqueous solution was added to the mixed solution, and after uniform dispersion, the solution was transferred to a 25 mL PTFE reactor. The reaction was carried out at 120 °C for 10 h in a constant temperature drying oven for a solvothermal reaction. After the reaction, the product was washed three times with ethanol and deionized water, and dried to obtain Na3(VO)2(PO4)2F@rGO powder.

[0128] (2) Na3(VO)2(PO4)2F@rGO, conductive carbon Super P, and binder PTFE in a mass ratio of 40-90:5-30:5-30 are ground into a granule in a quartz mortar; then, the electrode material is repeatedly rolled and pressed evenly using a roller mill, and then pressed onto a pretreated current collector. It is then dried in a vacuum drying oven, with the thickness of the electrode material controlled to 50 μm; the cycle performance of the electrode is as follows: Figure 10 As shown, the Coulomb efficiency for the first lap is 54.32%.

[0129] The above embodiments are merely examples. For instance, the interface layer can also be a stack of multiple materials.

[0130] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for constructing an artificial positive electrode electrolyte interface layer in an aqueous energy storage device, characterized in that, The method involves first depositing a nanometer-thick positive electrode electrolyte interface layer on the surface of the positive electrode sheet of the water-based energy storage device using atomic layer deposition, and then using the obtained positive electrode sheet with the interface layer as the positive electrode to build the water-based energy storage device. Among them, the electrolyte of the aqueous energy storage device is water as a solvent and contains at least one of lithium salt, sodium salt, potassium salt and zinc salt; The positive electrode sheet before the deposition of the positive electrode electrolyte interface layer is obtained by repeatedly rolling the electrode material until it is uniform and then pressing it onto the current collector. The electrode material includes a positive electrode active material, a conductive agent, and a binder. The positive electrode active material is Na3(VO)2(PO4)2F@rGO. The positive electrode sheet with the interface layer deposited also undergoes an electrochemical activation treatment, which is performed by cyclic charge-discharge treatment. The voltage range used during the charge-discharge process is 0.2V~1.2V. vs SCE, activation current is 0.1~5 C; Furthermore, the material of the positive electrode electrolyte interface layer is Al2O3. During the electrochemical activation process, Al2O3 can not only form stable ion diffusion channels, but also form new ionic compounds AlF3 through in-situ reactions, thereby improving the ion diffusion capacity and chemical stability of the interface layer.

2. The method as described in claim 1, characterized in that, The thickness of the positive electrode electrolyte interface layer is 2~25 nm.

3. The method as described in claim 2, characterized in that, The thickness of the positive electrode electrolyte interface layer is 20 nm.

4. The method as described in claim 1, characterized in that, The thickness of the electrode material located on the current collector is 10~80 μm; Both the rolling and pressing are performed using a double roller mill.

5. The method as described in claim 4, characterized in that, The conductive agent is conductive carbon Super P, and the binder is PTFE; in the electrode material, the mass ratio of the positive electrode active material, the conductive agent and the binder satisfies 40~90:5~30:5~30.

6. The method as described in claim 5, characterized in that, The operating voltage range is 0~1.5 V. vs SCE.

7. The method as described in claim 1, characterized in that, The current collector is one of titanium mesh, platinum mesh, or stainless steel mesh.

8. The method as described in claim 7, characterized in that, The current collector has also undergone a pretreatment process, namely, it is first polished with 1000-mesh metallographic sandpaper, then sonicated in 8wt%~30wt% hydrochloric acid for 15 minutes, and finally washed clean with ethanol.

9. The method as described in claim 7, characterized in that, The current collector is a 100-mesh titanium mesh.

10. The method as described in claim 1, characterized in that, The construction of the water-based energy storage device specifically involves assembling a negative electrode, an electrolyte, and a positive electrode, arranged in the order of negative electrode, electrolyte, and positive electrode.

11. The method as described in claim 10, characterized in that, The electrolyte is specifically one of the following: a sodium-containing polyacrylamide hydrogel electrolyte, a sodium-containing polyvinyl alcohol hydrogel electrolyte, or a sodium-containing carboxymethyl cellulose sodium hydrogel electrolyte.

12. The method as described in claim 10, characterized in that, The electrolyte is a sodium-containing polyacrylamide hydrogel electrolyte.

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