An internally connected cement-based supercapacitor and a method of making the same

Abstract

This invention discloses an internally tandem cement-based supercapacitor and its preparation method. The cement-based supercapacitor comprises one or more repeating units; each repeating unit includes a stacked cement-based electrolyte layer and a three-dimensional conductive unit layer; the three-dimensional conductive unit layer includes a three-dimensional porous conductive framework, divided into a lower porous electrode region, a middle ion-blocking conductive region, and an upper porous electrode region; the pores of the middle ion-blocking conductive region are densely filled with an insulating polymer, while the pores of the lower and upper porous electrode regions are loaded with electrochemically active materials; the outer peripheral sidewalls of the three-dimensional conductive unit layer are covered with in-situ mineralized ion-shielding rings to seal the ion short-circuit channels at the sidewall edges. The preparation method is compatible with the construction process of cement building components. This invention, through the design of the three-dimensional conductive unit layer and interface mineralization technology, achieves a synergistic multiplication of voltage window and energy density while effectively reducing the volume of the supercapacitor.

Description

Technical Field

[0001] This invention relates to the field of cement-based supercapacitor technology, and more specifically, to an internally connected cement-based supercapacitor and its preparation method. Background Technology

[0002] Currently, the discontinuity and instability of new energy power generation lead to frequent occurrences of "wind and solar curtailment." To increase the grid's buffer capacity and promote the local consumption of renewable energy, large-scale green energy storage buildings have emerged. Among them, cement-based supercapacitors, with their fast charge and discharge rates, good cycle stability, and integrated energy storage characteristics, have become an ideal choice for building energy storage.

[0003] However, existing cement-based supercapacitors still face some technical bottlenecks in practical applications, with narrow voltage windows and low energy density being two major limiting factors. The low voltage window means that a single cement-based supercapacitor cannot meet the driving requirements of high-voltage energy storage facilities; simultaneously, the low energy density severely limits the energy storage capacity per unit volume / area of ​​cement-based materials.

[0004] To address the aforementioned issues, constructing layered cement-based supercapacitors using a series connection is an effective way to overcome the dual bottlenecks of voltage and energy density. However, traditional external wire series connection methods are not only cumbersome and susceptible to corrosion damage from the building environment, but also result in a large overall supercapacitor size and high internal resistance due to the independent encapsulation of multiple individual cells. Although there are some research and development achievements in internally series-connected supercapacitors in existing technologies (see patent applications with publication numbers US20050262675A1 and CN108400017A), ion barrier encapsulation and electronic conduction between cells are often difficult to coexist, especially for cement-based supercapacitors, whose electrolyte is a cement matrix containing electrolyte, which has characteristics such as high hardness and rough surface, making it impossible for conventional polymer thin-film encapsulation layers to achieve effective encapsulation.

[0005] Therefore, how to design a novel cement-based supercapacitor that achieves internal series connection within a single package, effectively resolves the contradiction between ion blocking and electron conduction in a series system, and thus achieves a synergistic improvement in voltage window and energy density, is a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the aforementioned problems in existing technologies, the present invention aims to provide an internally connected cement-based supercapacitor and its preparation method. Through the design of a three-dimensional conductive unit layer and interface mineralization technology, the voltage window and energy density are synergistically multiplied while effectively reducing the volume of the supercapacitor.

[0007] To achieve the above objectives, in a first aspect, the present invention provides an internally connected cement-based supercapacitor, comprising a bottom electrode sheet, one or more repeating units, a first cement-based electrolyte layer, and a top electrode sheet stacked longitudinally within a single package; the repeating unit includes a stacked second cement-based electrolyte layer and a three-dimensional conductive unit layer; the three-dimensional conductive unit layer includes a three-dimensional porous conductive framework, which is longitudinally divided into a lower porous electrode region, a middle ion-blocking conductive region, and an upper porous electrode region; the pores of the middle ion-blocking conductive region are densely filled with an insulating polymer to block ion transport between the upper and lower cement-based electrolyte layers; the pores of the lower and upper porous electrode regions are interconnected and open, respectively loading electrochemically active materials and allowing adjacent cement-based electrolyte layers to infiltrate; the outer peripheral sidewalls of the three-dimensional conductive unit layer are covered with an in-situ mineralized ion shielding ring to seal the ion short-circuit channels at the edge of the sidewall.

[0008] This invention effectively resolves the contradiction between ion blocking and electronic conduction in an internal series system through a three-dimensional partitioned structure of a three-dimensional conductive unit layer: the central insulating region blocks ion transmission to prevent short circuits caused by communication between upper and lower electrolytes, while the continuous three-dimensional porous conductive framework provides a vertical electronic conduction path between the upper and lower units; the porous regions retained at the top and bottom increase the loading space of the active material on the one hand, and allow the fluid cement-based slurry to penetrate deeply on the other hand, forming an excellent mechanical interlock and low impedance interface after curing.

[0009] Further, the three-dimensional porous conductive framework is a foamed metal or a three-dimensional porous graphene aerogel with a thickness of 1 mm to 3 mm; the thickness of the insulating polymer filling the central ion-blocking conductive region accounts for 10% to 40% of the total thickness of the three-dimensional porous conductive framework; the thickness of the cement-based electrolyte layer is 1 mm to 5 mm. For example, the foamed metal is foamed nickel or foamed titanium with a thickness of 1 mm, 1.5 mm, 2 mm, 2.5 mm, or 3 mm; the thickness of the insulating polymer accounts for 10%, 20%, 30%, or 40% of the total thickness of the three-dimensional porous conductive framework. The thickness of the upper and lower porous electrode regions affects the amount of active material loaded on them, and the loading amount will affect the specific capacitance of the capacitor.

[0010] Furthermore, the ion shielding ring is composed of micro-expanded inorganic minerals generated in situ through a co-precipitation reaction between a mineralizing activator pre-coated on the outer peripheral sidewall of the three-dimensional conductive unit layer and free calcium ions seeping from the cement-based electrolyte layer. The in-situ generated ion shielding ring continuously covers the outer peripheral sidewall of the three-dimensional conductive unit layer and adheres to the inner wall of the supercapacitor mold or shell. Because it is generated through an in-situ reaction with free calcium ions seeping from the cement-based electrolyte layer, it effectively seals the capillary and coarse-pore ion short-circuit channels at the edge of the sidewall, while also possessing good mechanical strength and being less prone to detachment during cement curing.

[0011] Furthermore, the mineralization activator includes sodium sulfate or potassium sulfate, and the micro-expanded inorganic mineral is a calcium sulfate gypsum phase or a barium sulfate phase.

[0012] Furthermore, both the bottom and top electrode sheets employ a three-dimensional porous conductive framework, with electrochemically active materials loaded only on the side facing the cement-based electrolyte layer. This three-dimensional porous conductive framework loaded with electrochemically active materials allows the fluid cement-based slurry to penetrate deeply, forming excellent mechanical interlocking and a low-impedance interface after curing.

[0013] Furthermore, the cement-based electrolyte layer is a silicate cement-based composite material containing alkaline electrolyte, with a water-cement ratio of 0.3 to 0.5; the amount of alkaline electrolyte is 5 to 10% of the cement mass. For example, silicate cement is a common commercially available building material, the water-cement ratio of the cement is 0.3, 0.4, or 0.5, and the amount of alkaline electrolyte is 5%, 6%, 7%, 8%, 9%, or 10% of the cement mass.

[0014] Further, the electrochemical active material is one or more of capacitive electrode materials and pseudocapacitive electrode materials. As one embodiment, the cement-based supercapacitor adopts a symmetrical system, where both its positive and negative electrode active materials are the same capacitive electrode material (such as activated carbon or reduced graphene oxide); the lower and upper porous electrode regions of the three-dimensional conductive unit layer are filled with capacitive materials. As another embodiment, the cement-based supercapacitor adopts an asymmetrical system, where its positive electrode active material is a pseudocapacitive electrode material such as nickel-cobalt layered double hydroxide, and its negative electrode active material is a capacitive electrode material such as activated carbon; the pseudocapacitive electrode material such as nickel-cobalt layered double hydroxide is loaded on the surface of the lower porous electrode region of the three-dimensional conductive unit layer, serving as the positive electrode of the bottom capacitor cell; the pores of the upper porous electrode region of the three-dimensional conductive unit layer are filled with capacitive electrode materials such as activated carbon, serving as the negative electrode of the top capacitor cell.

[0015] Secondly, the present invention provides a method for preparing an internally connected series cement-based supercapacitor, used to prepare the cement-based supercapacitor as described above, comprising:

[0016] S1. After uniformly arranging sacrificial templates on the upper and lower surfaces of a three-dimensional porous conductive framework, the framework is placed in a sealed container and impregnated with an insulating polymer under vacuum. After thermosetting the insulating polymer and eluting the template, a three-dimensional conductive unit layer with an upper porous electrode region, a middle ion-blocking conductive region, and a lower porous electrode region is obtained.

[0017] S2. Electrochemically active materials are loaded in the upper porous electrode region, lower porous electrode region, bottom electrode sheet, and top electrode sheet of the three-dimensional conductive unit layer. For example, the loading is carried out by electrodeposition or filling with an active material slurry; the electrochemically active materials are loaded on the inner side of the bottom electrode sheet and the top electrode sheet.

[0018] S3. A solution containing a mineralizing activator is uniformly coated on the outer peripheral sidewall of the three-dimensional conductive unit layer, and then dried and cured.

[0019] S4. First, lay the bottom electrode sheet (load side up) flat in the mold from bottom to top. Then, pour the cement-based electrolyte slurry, vibrate to vent air, and lay it into the three-dimensional conductive unit layer to form one or more repeating units. Finally, cover the cement-based electrolyte layer and the top electrode sheet (load side down).

[0020] S5. Place in a curing room to cure and demold to obtain a cement-based supercapacitor connected in series internally.

[0021] The layered vibration casting process used in the above preparation method is highly compatible with the construction technology of modern building cement components and has high practical value.

[0022] Further, in step S1, water-soluble salt particles are mixed with a volatile solvent containing a polymer binder to prepare a salt slurry; the salt slurry is coated onto the upper and lower surfaces of the three-dimensional porous conductive framework, with a coating depth of 30% to 45% of the total thickness, and the volatile solvent solidifies to form a sacrificial template; after the insulating polymer in the central region has cured, the sacrificial template is washed away in an aqueous solvent, opening the pores in the upper and lower porous electrode regions. For example, the water-soluble salt particles are NaCl, the polymer binder is polyethylene glycol, and the insulating polymer is alkali-resistant bisphenol-type epoxy resin or polyurethane elastomer.

[0023] Further, in step S3, the solution containing the mineralization activator is a thickened sodium sulfate or potassium sulfate solution; in step S4, the sodium sulfate or potassium sulfate undergoes a co-precipitation reaction with free calcium ions in the cement-based electrolyte layer, and the in-situ generated calcium sulfate gypsum phase or barium sulfate phase seals the ion short-circuit channels at the edge of the capacitor sidewall. For example, the sodium sulfate or potassium sulfate solution is thickened using sodium alginate.

[0024] It is understandable that the pouring and curing temperatures in the above preparation methods can be at room temperature, and the process parameters such as pouring and curing times can be reasonably determined based on the uniformity or curing effect. The vacuum degree and soaking time in vacuum impregnation can be reasonably determined based on the adsorption effect of the solution.

[0025] Compared with the prior art, the present invention has the following technical effects:

[0026] (1) By introducing a three-dimensional conductive unit layer that combines electronic conduction and ion blocking functions, the present invention enables the cement-based supercapacitor to achieve longitudinal layered physical series connection within a single package, effectively replacing the traditional cumbersome external wiring scheme and greatly improving the reliability and volume utilization of the structural energy storage supercapacitor in the building environment.

[0027] (2) The present invention proposes an adaptive in-situ crystallization ion shielding ring design, which utilizes the free calcium ions released by the hydration of cement matrix and the activator to generate micro-expansion minerals in situ at the edge of the repeating unit, intelligently sealing the coarse pores and even capillary leakage channels at the interface edge, fundamentally eliminating the internal short circuit phenomenon that is prone to occur in multi-monomer series.

[0028] (3) Through its internally connected multilayer structure design, this invention not only integrates energy storage and allows for flexible adjustment of the capacitor unit area and the number of series layers according to actual application needs, but also achieves a synergistic improvement in the voltage window and energy density of cement-based supercapacitors. For example, the voltage window of the symmetrical layered cement-based supercapacitor is increased from 1 V for a single layer to 3 V for three layers in series, and the voltage window of the asymmetrical layered cement-based supercapacitor is increased from 1.5 V for a single layer to 4.5 V for three layers in series, achieving a linear expansion of the voltage window. With the support of the voltage effect, the energy density of both symmetrical and asymmetrical multilayer supercapacitors is significantly increased to 3.11 times that of a single layer (0.59 mWh / cm² for the symmetrical type). 2 The asymmetric type reaches 1.12 mWh / cm³. 2 ).

[0029] (4) The layered vibration casting process used in the preparation method of the present invention is highly compatible with the construction process of modern building cement components and has high practical value. Attached Figure Description

[0030] The invention, its features and advantages will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0031] Figure 1 This is a schematic diagram of the internal series-connected cement-based supercapacitor in this invention.

[0032] Figure 2 This is a schematic diagram of the structure of the three-dimensional conductive unit layer and ion shielding ring in this invention.

[0033] Figure 3 Cyclic voltammetry curves of supercapacitors at a scan rate of 10 mV / s were prepared for Comparative Example 1, Example 1, and Example 2.

[0034] Figure 4 To prepare supercapacitors at 2 mA / cm² for Comparative Example 1, Examples 1 and 22 Constant current charge-discharge curves at current density.

[0035] Figure 5 (a) Preparation of a 2 mA / cm supercapacitor for Comparative Example 1, Examples 1 and 2 2 Area ratio capacitance under current density; Figure 5 (b) Preparation of a 2 mA / cm supercapacitor for Comparative Example 1, Examples 1 and 2 2 Energy density at current density.

[0036] Figure 6 Cyclic voltammetry curves of supercapacitors at a scan rate of 10 mV / s were prepared for Comparative Examples 2, 3, and 4.

[0037] Figure 7 To prepare supercapacitors at 2 mA / cm² for Comparative Examples 2, 3, and 4 2 Constant current charge-discharge curves at current density.

[0038] Figure 8 (a) Preparation of a 2 mA / cm supercapacitor for Comparative Examples 2, 3, and 4 2 Area ratio capacitance under current density; Figure 8 (b) Preparation of a 2 mA / cm supercapacitor for Comparative Examples 2, 3, and 4 2 Energy density at current density.

[0039] Reference numerals: 1. Bottom electrode sheet; 2. Repeating unit; 3. First cement-based electrolyte layer; 4. Top electrode sheet; 5. Ion shielding ring; 21. Second cement-based electrolyte layer; 22. Three-dimensional conductive unit layer; 221. Lower porous electrode region; 222. Middle ion-blocking conductive region; 223. Upper porous electrode region. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but these are not intended to limit the scope of the invention.

[0041] In the description of this application, the terms "upper", "lower", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and do not require the present invention to be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0042] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0043] The reagents, thickeners, and solvents used in the following examples are all commercially available. The foam metal was purchased from Suzhou Taili Materials Technology Co., Ltd., and the silicate cement was purchased from Anhui Conch Cement Co., Ltd. The detection methods used are existing technologies that can be found online. The electrochemical performance testing mainly used a CHI660E electrochemical workstation for cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) testing.

[0044] See Figure 1 and Figure 2 The present invention provides an internally connected cement-based supercapacitor, wherein a bottom electrode sheet 1, one or more repeating units 2, a first cement-based electrolyte layer 3 and a top electrode sheet 4 are stacked longitudinally in a single package; the repeating unit 2 includes a stacked second cement-based electrolyte layer 21 and a three-dimensional conductive unit layer 22.

[0045] The three-dimensional conductive unit layer 22 includes a three-dimensional porous conductive framework, which is divided longitudinally into a lower porous electrode region 221, a middle ion-blocking conductive region 222, and an upper porous electrode region 223. The pores of the middle ion-blocking conductive region 222 are densely filled with insulating polymer, blocking ion transport between the upper and lower cement-based electrolyte layers. The pores of the lower porous electrode region 221 and the upper porous electrode region 223 are interconnected and open, respectively loading electrochemically active materials and allowing adjacent cement-based electrolyte layers to infiltrate.

[0046] The outer peripheral sidewall of the three-dimensional conductive unit layer 22 is covered with an in-situ mineralized ion shielding ring 5 to seal the ion short-circuit channel at the edge of the sidewall.

[0047] Example 1

[0048] This embodiment demonstrates the fabrication of a double-layer symmetrical cement-based supercapacitor. The fabrication steps are as follows:

[0049] (1) Select nickel foam with a thickness of 1.5 mm and a porosity of 90%, and cut it into a shape of 1 cm × 1 cm. Mix NaCl particles with anhydrous ethanol containing 5 wt% polyethylene glycol (PEG-400) and grind to prepare a high-viscosity salt slurry. Use a scraper to evenly coat the salt slurry onto the upper and lower surfaces of the nickel foam with a thickness of 0.5 mm. After the ethanol evaporates at 60 ℃ to form a sacrificial template, place it in a sealed vacuum impregnation tank and inject bisphenol A type epoxy resin. Evaporate the tank to -0.09 MPa so that the resin fills the remaining 0.5 mm voids in the center of the nickel foam. After curing at 80 ℃ for 4 h, place it in a 60 ℃ ultrasonic water bath for 60 min to wash away the sacrificial template and obtain a three-dimensional porous conductive framework with porous upper and lower surfaces and an insulating middle part.

[0050] (2) Activated carbon, conductive carbon black, and polyvinylidene fluoride were mixed in a mass ratio of 8:1:1, and N-methylpyrrolidone was added. The mixture was ultrasonicated for 20 min and then stirred continuously until a uniform slurry was formed. The slurry was then uniformly compacted and filled into the upper porous region (A side) and lower porous region (B side) of the above-mentioned three-dimensional porous conductive framework, and dried in an oven at 60 °C for 12 h. Simultaneously, the slurry was coated on one side of nickel foam as bottom and top electrode sheets.

[0051] (3) Edge mineralization coating treatment: Prepare a 2.0 mol / L saturated sodium sulfate aqueous solution containing 1 wt% sodium alginate as a thickener, and use a coating brush to fully coat it on the outer peripheral sidewall of the double-sided skeleton. Dry and cure to form an ion shielding ring for subsequent adaptive in-situ mineralization, and obtain a symmetrical three-dimensional conductive unit layer.

[0052] (4) Weigh 5 g of potassium hydroxide and 40 g of deionized water, mix them evenly, and then place them together with 100 g of cement in a cement slurry mixing pot. Stir evenly for 10 min to obtain a cement-based electrolyte slurry. Lay a bottom electrode sheet loaded with activated carbon (activated carbon side up) flat at the bottom of a 1 cm × 1 cm mold, pour a 2 mm thick first layer of cement-based electrolyte slurry, and vibrate to remove air. When the first layer of cement-based electrolyte slurry maintains good fluidity, lay the above-mentioned symmetrical three-dimensional conductive unit layer on the slurry as a repeating unit.

[0053] (5) Subsequently, a second layer of cement-based electrolyte slurry, 2 mm thick, was poured to cover the top electrode sheet (activated carbon side down). It was then placed in a curing room at 20 ℃ and 95% relative humidity for 28 days. After demolding, a sheet with an area of ​​1 cm² was obtained. 2 A double-layer symmetrical internal series cement-based supercapacitor.

[0054] Example 2

[0055] This embodiment fabricates a three-layer symmetrical internally tandem cement-based supercapacitor. The fabrication steps are similar to those in Embodiment 1, except that two repeating units from Embodiment 1 are introduced. After the first layer of cement-based electrolyte slurry, a first symmetrical three-dimensional conductive unit layer is laid flat. After pouring the second layer of cement-based electrolyte slurry, a second symmetrical three-dimensional conductive unit layer is laid flat. Then, a 2 mm thick top layer of cement-based electrolyte slurry is poured, and finally, the top electrode sheet is covered. The mold and material dimensions are 1 cm × 1 cm, and the fabrication area is 1 cm². 2 A three-layer symmetrical internal series supercapacitor.

[0056] Example 3

[0057] This embodiment describes the fabrication of a double-layer asymmetric internally tandem cement-based supercapacitor. The fabrication steps are as follows:

[0058] (1) The preparation of the three-dimensional conductive framework is the same as step (1) in Example 1.

[0059] (2) A nickel-cobalt layered double hydroxide positive electrode was loaded using an electrodeposition method. The electrodeposition solution was prepared by nickel nitrate solution and cobalt nitrate solution, both with a concentration of 0.08 mol / L and a volume ratio of 5:6. The upper surface (B side) of the three-dimensional conductive framework was densely shielded with insulating tape, and the lower surface (A side) was immersed in the electrodeposition solution. Cyclic voltammetry was used, with a voltage range of -1.5 V to -0.9 V, a scan rate of 10 mV / s, and 20 scans to deposit nickel-cobalt layered double hydroxide on the A side. The electrode was then dried in an oven at 60 ℃ for 12 h. Simultaneously, the nickel-cobalt layered double hydroxide was deposited on one side in nickel foam as the top electrode sheet; the upper surface (B side) was filled with the activated carbon slurry from Example 1 to obtain an asymmetric three-dimensional conductive unit layer. The bottom nickel foam was filled with the activated carbon slurry from Example 1 as the bottom electrode sheet.

[0060] (3) The edge mineralization coating treatment is the same as in Example 1.

[0061] (4) Lay a bottom electrode sheet loaded with activated carbon (activated carbon side up) at the bottom of a 1 cm × 1 cm mold, and pour a 2 mm first layer of cement-based electrolyte slurry; lay an asymmetric three-dimensional conductive unit layer (nickel-cobalt layered double hydroxide side down as the bottom positive electrode, activated carbon side up as the top negative electrode) as a repeating unit.

[0062] (5) Pour a second layer of 2 mm cement-based electrolyte slurry to cover the top electrode sheet (facing down) loaded with nickel-cobalt material. Demold after 28 days of standard curing to obtain an area of ​​1 cm². 2 A double-layer asymmetric internal series cement-based supercapacitor.

[0063] Example 4

[0064] This embodiment prepares a three-layer asymmetric internal series cement-based supercapacitor for energy storage. The preparation steps are similar to those in Embodiment 3. The difference from Embodiment 3 is that two repeating units from Embodiment 3 are introduced to cast a total of three cement-based electrolyte layers.

[0065] Comparative Example 1

[0066] This embodiment fabricates a single-layer symmetrical cement-based supercapacitor. The difference between this fabrication method and that of Embodiment 1 is that no three-dimensional conductive unit layer is added. Instead, a 2 mm thick single-layer cement-based electrolyte slurry is poured onto the bottom electrode sheet and then directly covered to form a single-layer symmetrical supercapacitor.

[0067] Comparative Example 2

[0068] This embodiment fabricates a single-layer asymmetric cement-based supercapacitor. The difference between this fabrication method and that of Example 3 is that no three-dimensional conductive unit layer is added. Instead, a 2 mm thick single-layer cement-based electrolyte slurry is poured onto the bottom electrode sheet and then directly covered to form a single-layer asymmetric cement-based supercapacitor.

[0069] The areal capacitance C (mF / cm²) of cement-based supercapacitors 2 The result is obtained by formula (1):

[0070] C=(I·Δt) / (S·ΔV) (1)

[0071] Wherein, I (mA / cm 2 ) represents the current density during the charging and discharging process, Δt (s) represents the discharge time, and S (cm) represents the current density during the charging and discharging process. 2 ) represents the contact area, and ΔV(V) represents the voltage window.

[0072] Energy density E (mWh / cm³) 2 It can be calculated using formula (2):

[0073] E=(C·ΔV 2 ) / 7200 (2)

[0074] Where ΔV(V) represents the voltage window of the supercapacitor.

[0075] from Figure 3 As can be seen, the CV curves of all symmetrical supercapacitors exhibit approximately rectangular shapes and lack obvious redox peaks. Combined with... Figure 4 From the single-layer comparative example 1 to the double-layer example 1, and then to the triple-layer example 2, the voltage window of the supercapacitor expands linearly, increasing from 1 V for the single layer to 2 V and 3 V after series connection.

[0076] from Figure 5As can be seen from this, at 2 mA / cm 2 At current density, as the number of layers increases, the areal capacitance of the supercapacitor increases from 1526.3 mF / cm². 2 It decreased to 512.1 mF / cm 2 This is because the series connection of supercapacitors leads to a decrease in the area-to-capacitance ratio. However, the energy density of supercapacitors increases with the number of layers, which is consistent with the energy density calculation formula. As shown in formula (2), the energy density is proportional to the square of the voltage, which means that the voltage has a more significant impact on the energy density than the capacitance. Even a small increase in voltage can lead to a significant increase in energy density. As the number of layers increases, the voltage of the supercapacitor increases from 1 V to 3 V. Calculations show that from the single-layer comparative example 1 to the three-layer example 2, the energy density increases from 0.19 mWh / cm³. 2 It jumped significantly to 0.59 mWh / cm 2 (Increased to 3.11 times).

[0077] from Figure 6 As can be seen, all asymmetric supercapacitors exhibit significant redox peaks, indicating that the electrode materials underwent typical Faraday redox reactions. Combined with... Figure 7 and Figure 8 From the single-layer comparative example 2 to the three-layer series example 4, the voltage window increased exponentially from 1.5 V to 4.5 V, and the energy density increased from 0.36 mWh / cm³. 2 It jumped to 1.12 mWh / cm 2 (Also increased to 3.11 times).

[0078] As can be seen from the above description, by using internal series connection and layer design, the energy density and voltage window of layered cement-based supercapacitors can be effectively improved without significantly increasing the device size, thus achieving synergistic optimization of energy storage performance.

[0079] Those skilled in the art should understand that variations can be implemented by combining existing technology with the above embodiments, which will not be elaborated here. Such variations do not affect the essence of the present invention, and will not be elaborated here either.

[0080] The preferred embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above. Systems and structures not described in detail should be understood as being implemented in a conventional manner in the art. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the present invention. This does not affect the essential content of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the present invention are still within the scope of protection of the present invention.

Claims

1. A cement-based supercapacitor connected in series internally, characterized in that: Within a single package, a bottom electrode sheet, one or more repeating units, a first cement-based electrolyte layer, and a top electrode sheet are stacked vertically in sequence. The repeating unit includes a stacked second cement-based electrolyte layer and a three-dimensional conductive unit layer; The three-dimensional conductive unit layer includes a three-dimensional porous conductive framework, which is divided into a lower porous electrode region, a middle ion-blocking conductive region, and an upper porous electrode region along the longitudinal direction. The pores of the middle ion-blocking conductive region are densely filled with insulating polymer, blocking ion transport between the upper and lower cement-based electrolyte layers. The pores of the lower and upper porous electrode regions are interconnected and open, respectively loading electrochemically active materials and allowing adjacent cement-based electrolyte layers to infiltrate. The outer peripheral sidewall of the three-dimensional conductive unit layer is covered with an in-situ mineralized ion shielding ring to seal the ion short-circuit channel at the edge of the sidewall.

2. The cement-based supercapacitor with internal series connection according to claim 1, characterized in that, The three-dimensional porous conductive framework is a foamed metal or a three-dimensional porous graphene aerogel with a thickness of 1 mm to 3 mm; the thickness of the insulating polymer filling the central ion-blocking conductive region accounts for 10% to 40% of the total thickness of the three-dimensional porous conductive framework; the thickness of the cement-based electrolyte layer is 1 mm to 5 mm.

3. The cement-based supercapacitor with internal series connection according to claim 1, characterized in that, The ion shielding ring is composed of micro-expanded inorganic minerals generated in situ by a co-precipitation reaction between a mineralizing activator pre-coated on the outer peripheral sidewall of the three-dimensional conductive unit layer and free calcium ions seeping from the cement-based electrolyte layer.

4. A cement-based supercapacitor connected in series internally according to claim 3, characterized in that, The mineralization activator includes sodium sulfate or potassium sulfate, and the micro-expanded inorganic mineral is calcium sulfate gypsum phase or barium sulfate phase.

5. A cement-based supercapacitor connected in series internally according to claim 1, characterized in that, Both the bottom and top electrode sheets employ a three-dimensional porous conductive framework, with electrochemically active materials loaded only on the side of the cement-based electrolyte layer facing the pores.

6. A cement-based supercapacitor connected in series internally according to claim 1, characterized in that, The cement-based electrolyte layer is a silicate cement-based composite material containing alkaline electrolyte, with a water-cement ratio of 0.3 to 0.5; the amount of alkaline electrolyte is 5 to 10% of the cement mass.

7. A cement-based supercapacitor connected in series internally according to claim 1, characterized in that, The electrochemically active material is one or more of capacitive electrode materials and pseudocapacitive electrode materials.

8. A method for preparing an internally connected series cement-based supercapacitor, characterized in that, The method for preparing the cement-based supercapacitor as described in any one of claims 1 to 7 comprises: S1. After uniformly arranging sacrificial templates on the upper and lower surfaces of a three-dimensional porous conductive framework, the framework is placed in a sealed container and impregnated with an insulating polymer under vacuum. After thermosetting the insulating polymer and eluting the template, a three-dimensional conductive unit layer with an upper porous electrode region, a middle ion-blocking conductive region, and a lower porous electrode region is obtained. S2. Electrochemically active materials are loaded in the upper porous electrode region, the lower porous electrode region, the bottom electrode sheet, and the top electrode sheet of the three-dimensional conductive unit layer. S3. A solution containing a mineralizing activator is uniformly coated on the outer peripheral sidewall of the three-dimensional conductive unit layer, and then dried and cured. S4. First, lay the bottom electrode sheet flat in the mold from bottom to top. Then, pour the cement-based electrolyte slurry, vibrate to vent the air, and lay it into the three-dimensional conductive unit layer to form one or more repeating units. Finally, cover the cement-based electrolyte layer and the top electrode sheet. S5. Place in a curing room to cure and demold to obtain a cement-based supercapacitor connected in series internally.

9. The method for preparing an internally connected cement-based supercapacitor according to claim 8, characterized in that, In step S1, water-soluble salt particles are mixed with a volatile solvent containing a polymer binder to form a salt slurry; the salt slurry is coated on the upper and lower surfaces of the three-dimensional porous conductive framework, with a coating depth of 30% to 45% of the total thickness, and the volatile solvent is used to solidify and form a sacrificial template; after the insulating polymer in the central region has solidified, the sacrificial template is washed off in an aqueous solvent, so that the pores of the upper and lower porous electrode regions are opened.

10. The method for preparing an internally connected cement-based supercapacitor according to claim 8, characterized in that, The solution containing mineralization activator applied in step S3 is a thickened sodium sulfate or potassium sulfate solution; in step S4, sodium sulfate or potassium sulfate undergoes a co-precipitation reaction with free calcium ions in the cement-based electrolyte layer, and the calcium sulfate gypsum phase or barium sulfate phase generated in situ seals the ion short-circuit channels at the edge of the capacitor sidewall.

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