Flexible potassium ion micro battery and preparation method thereof

Abstract

The invention belongs to the technical field of energy storage, and particularly relates to a micro battery technology, in particular to a flexible potassium ion micro battery and a preparation method thereof. The invention provides a flexible potassium ion micro battery. The flexible potassium ion micro battery is mainly composed of a KFeMnHCF (iron substituted manganese-rich Prussian blue) positive electrode, a PTCDI / MXene negative electrode and a KCF3SO3-PAM (potassium trifluoromethanesulfonate-polyacrylamide) hydrogel electrolyte. According to the technical scheme, compared with a traditional lithium ion micro battery, the lithium ion micro battery has better electrochemical performance, and the ultra-high cycle life of 89.17% is achieved after 2500 GCD cycles under 5.0 mA cm <-2 >. And relatively high energy density (202.81 [mu] Wh cm <-2 >) and power density (7.99 mW cm <-2 >). The flexible potassium ion micro battery has the characteristics of high safety, miniaturization and low cost, so that the flexible potassium ion micro battery can be more conveniently applied to wearable equipment and integrated electronic products, and has a wide application prospect in energy storage equipment.

Description

Technical Field

[0001] The present invention belongs to the field of energy storage technology, specifically relates to micro battery technology, and in particular to a flexible potassium ion micro battery and a preparation method thereof. Background Art

[0002] With the rapid development of information technology, especially the popularization of portable electronic devices and wearable technology, new requirements have been put forward for energy storage. Although traditional lithium-ion batteries have excellent performance in energy density and cycle stability, they are usually not flexible and deformable due to the use of rigid packaging materials such as metal casings or plastic packaging. This limits the application of lithium-ion batteries in some emerging fields, such as smart watches, health monitors and other devices that require high integration and have bending or folding characteristics.

[0003] At the same time, researchers began to explore technical solutions to replace lithium-ion batteries to overcome the above limitations. Potassium-ion batteries have gradually attracted people's interest as a potential candidate. Potassium (K) elements are more widely distributed around the world and have relatively low mining costs, which gives potassium-ion batteries obvious economic advantages in large-scale commercial production. In addition, potassium metal has a very low redox potential (-2.93 V vs. SHE), indicating its potential for high voltage in battery applications.

[0004] However, to achieve high-performance potassium-ion microbatteries, a series of technical challenges need to be solved. For example, how to increase the energy density of the battery, extend the cycle life, and improve the charge and discharge rate. At the same time, in order to meet the needs of flexibility, the battery components must be able to withstand repeated mechanical stress without affecting their performance. Summary of the invention

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides a flexible potassium ion microbattery with high cycle life, high energy density and power density, high voltage, excellent flexibility, high safety, variable specifications and low price, and a preparation method thereof. Specifically, the present invention adopts the following technical solutions:

[0006] First, the flexible potassium ion microbattery provided by the present invention is mainly composed of a KFeMnHCF (iron-substituted manganese-rich Prussian blue) positive electrode, a PTCDI / MXene negative electrode and a KCF3SO3-PAM (potassium trifluoromethanesulfonate-polyacrylamide) hydrogel electrolyte. The KFeMnHCF positive electrode and the PTCDI / MXene negative electrode are preferably interdigitated electrodes, and the KCF3SO3-PAM hydrogel electrolyte is between the positive and negative electrodes.

[0007] For the flexible potassium ion microbattery described in the present invention, preferably, the preparation method of the KFeMnHCF positive electrode is: use K4Fe(CN)6·3H2O, FeSO4·7H2O and MnSO4·H2O as raw materials for mixed reaction to obtain a precipitate, and then thoroughly wash and dry with deionized water and peel off to obtain KFeMnHCF material, and then treat to obtain the KFeMnHCF positive electrode.

[0008] Furthermore, as a more preferred scheme, the preparation method of the KFeMnHCF positive electrode is: dissolving K4Fe(CN)6·3H2O, FeSO4·7H2O and MnSO4·H2O in saturated KCl solution respectively, and then slowly dropping FeSO4·7H2O and MnSO4·H2O solutions into K4Fe(CN)6·3H2O solution under magnetic stirring, centrifuging the formed precipitate and thoroughly washing and drying it with deionized water, and then peeling it to obtain a KFeMnHCF filter cake, and laser engraving the KFeMnHCF filter cake into interdigital electrodes to obtain a KFeMnHCF positive electrode.

[0009] In the preparation method of the KFeMnHCF positive electrode, preferably, the molar ratio of K4Fe(CN)6·3H2O, FeSO4·7H2O and MnSO4·H2O is 2:(1-2):(6-7), more preferably 2:(1.1-1.8):(6.2-7), further preferably 2:(1.3-1.6):(6.5-6.7), and most preferably 2:1.5:6.5.

[0010] In the preparation method of the KFeMnHCF positive electrode, preferably, the K4Fe(CN)6·3H2O, FeSO4·7H2O and MnSO4·H2O are respectively dissolved in a saturated KCl solution, and the volume ratio of the saturated KCl solution of K4Fe(CN)6·3H2O, FeSO4·7H2O and MnSO4·H2O is preferably 5:5:4; the magnetic stirring temperature is 60-70°C, and the magnetic stirring time is 8-12h; the drying temperature is 60-80°C, and the drying time is 8-12h.

[0011] For the flexible potassium ion microbattery described in the present invention, preferably, the preparation method of the PTCDI / MXene negative electrode is: adding PTCDI (3,4,9,10-perylenetetracarboxylic acid diimide) and MXene to a DMF solution to form a uniform mixed solution, then vacuum filtering and drying to obtain a PTCDI / MXene material, and laser engraving the PTCDI / MXene material into interdigitated electrodes to obtain a PTCDI / MXene negative electrode.

[0012] In the preparation method of the PTCDI / MXene negative electrode, preferably, the mass ratio of PTCDI to MXene is 7-9:1-3, more preferably 9:1; the filter membrane used for the vacuum filtration is a 0.22 μm nylon membrane; the vacuum drying temperature is 40-45° C., and the drying time is 1-2 h.

[0013] For the flexible potassium ion microbattery described in the present invention, preferably, the preparation method of the KCF3SO3-PAM hydrogel electrolyte is: acrylamide, K2S2O8 and N,N′-methylenebisacrylamide are added to deionized water in sequence, and then the mixture is stirred evenly and injected into a glass model for vacuum drying, and finally the prepared hydrogel film is immersed in a KCF3SO3 aqueous solution to reach a equilibrium state.

[0014] Furthermore, in the preparation method of the KCF3SO3-PAM hydrogel electrolyte, preferably, the mass ratio of acrylamide, K2S2O8 and N,N′-methylenebisacrylamide is 3-4:0.03-0.04:0.004-0.005; the stirring time is 1-2h; the drying is vacuum drying at a temperature of 70-80°C for 1-2h; the concentration of the KCF3SO3 aqueous solution is 22-25mol·L -1 .

[0015] Secondly, the present invention also provides a method for preparing the above-mentioned flexible potassium ion microbattery, which is to transfer the KFeMnHCF positive electrode and the PTCDI / MXene negative electrode to a flexible substrate, and apply KCF3SO3-PAM hydrogel electrolyte to obtain a flexible potassium ion microbattery; the substrate can be a polyethylene terephthalate (PET) film, a polydimethylsiloxane (PDMS) film, a polyimide (PI) film, a polyetherimide (PEI) film, etc.

[0016] The flexible potassium ion microbattery conceived by the present invention has the following beneficial effects:

[0017] (1) The flexible potassium ion microbattery of the present invention has excellent electrochemical performance at 5.0 mA cm -2 The ultra-high cycle life of 89.17% after 2500 GCD cycles.

[0018] (2) The flexible potassium ion microbattery of the present invention has a high energy density (202.81 μWh cm -2 ) and power density (7.99 mW cm -2 ).

[0019] (3) The flexible potassium ion microbattery of the present invention has a relatively high voltage, up to 2.6 V.

[0020] (4) The flexible potassium-ion microbattery of the present invention has better flexibility than traditional lithium-ion microbatteries and can still maintain 95.13% of its initial capacity when bent 180°.

[0021] (5) The flexible potassium ion microbattery of the present invention is safer than traditional lithium ion microbatteries. Traditional microbatteries usually use organic solvents as electrolytes, which are flammable and explosive. The aqueous electrolyte of the present invention does not pose any serious danger.

[0022] (6) The flexible potassium ion microbattery of the present invention has a smaller size and a variety of specifications compared to traditional lithium ion microbatteries.

[0023] (7) The flexible potassium ion microbattery of the present invention has a simpler preparation process and lower cost than the traditional lithium ion microbattery. The microbattery of the present invention is more convenient to use in wearable devices and integrated electronic products due to its high safety, miniaturization and low cost, and has broad application prospects as an energy storage device. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a structural diagram of a flexible potassium ion microbattery of the present invention;

[0025] Figure 2 The SEM images of the KFeMnHCF positive electrode and the PTCDI / MXene negative electrode of a flexible potassium ion microbattery of the present invention show the micro size of KFeMnHCF and PTCDI / MXene;

[0026] Figure 3 The PTCDI / MXene negative electrode of a flexible potassium ion microbattery of the present invention is scanned at a rate of 2mVs -1 When the CV curves of the PTCDI / MXene negative electrode obtained with different PTCDI and MXene ratios are 9:1, the current density and area are large, and the redox peak is obvious. The performance is better when the PTCDI / MXene ratio is 9:1.

[0027] Figure 4 A flexible potassium ion microbattery of the present invention is provided at a scan rate of 1 mV s -1 The CV curve at , the current density and area are large, and the redox peak is obvious;

[0028] Figure 5 The relationship curve between the specific capacity and Coulomb efficiency of a flexible potassium ion microbattery of the present invention and the number of cycles is shown in Figure 2. The charge and discharge current density is 5.0 mA cm -2After 2500 cycles, the capacity retention rate still reached 89.17%, and the Coulombic efficiency was extremely high;

[0029] Figure 6 A schematic diagram of a flexible potassium ion microbattery of the present invention driving a single LED bulb;

[0030] Figure 7 A schematic diagram of an integrated system of a flexible potassium ion microbattery and a MXene sponge pressure sensor of the present invention;

[0031] Figure 8 The relationship between the current and time of a pressure sensor driven by a single or multiple series-connected flexible potassium ion microbattery under the same stress of the present invention is shown. The results show that when a certain pressure is applied to the pressure sensor under the drive of two or three microbatteries, the current is two or three times that of a single microbattery driving current;

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] A method for preparing a flexible potassium ion microbattery according to an embodiment of the present invention comprises the following steps:

[0034] (1) Preparation of KFeMnHCF positive electrode.

[0035] (2) Preparation of PTCDI / MXene negative electrode.

[0036] (3) Preparation of KCF3SO3-PAM hydrogel electrolyte.

[0037] (4) Encapsulating flexible potassium-ion microbatteries.

[0038] Example 1

[0039] In a preferred embodiment of the present invention, a novel method for preparing a flexible potassium ion microbattery comprises the following steps:

[0040] (1) Preparation of KFeMnHCF positive electrode.

[0041] 2mmol K4Fe(CN)6·3H2O, 1.5mmol FeSO4·7H2O and 6.5mmol MnSO4·H2O were dissolved in saturated KCl solution, the volume ratio of 2mmol K4Fe(CN)6·3H2O, 1.5mmol FeSO4·7H2O and 6.5mmol MnSO4·H2O saturated KCl solution was 5:5:4 respectively, and then heated at 60 ° Under magnetic stirring at 80 °C, FeSO4·7H2O and MnSO4·H2O solutions were slowly added to K4Fe(CN)6·3H2O solution. After 12 h, the formed precipitate was centrifuged and thoroughly washed with deionized water. ° After drying in air at 400 °C for 12 h, a KFeMnHCF filter cake was obtained, which was laser engraved into interdigitated electrodes to finally prepare the KFeMnHCF positive electrode.

[0042] (2) Preparation of PTCDI / MXene negative electrode.

[0043] 90 mg PTCDI and 10 mg MXene were added to 5 ml DMF solution and ultrasonically crushed to obtain a uniform mixed solution. The mixed solution was vacuum filtered and then vacuum dried at 40 °C for 1 h to obtain a PTCDI / MXene filter cake. The PTCDI / MXene filter cake was laser engraved into interdigitated electrodes to finally obtain a PTCDI / MXene negative electrode.

[0044] (3) Preparation of KCF3SO3-PAM hydrogel electrolyte.

[0045] 3 g acrylamide, 30 mg K2S2O8 and 4 mg N,N′-methylenebisacrylamide were added to 20 ml deionized water in sequence. The mixture was then stirred for 1 h and poured into a glass mold. ° C in an oven for 1 h. Finally, the prepared PAM hydrogel film was immersed in 22 mol· L -1 The KCF3SO3 aqueous solution reached equilibrium after 12 hours, and finally obtained KCF3SO3-PAM hydrogel electrolyte.

[0046] (4) Encapsulating flexible potassium-ion microbatteries.

[0047] The KFeMnHCF positive electrode and PTCDI / MXene negative electrode were transferred to the PDMS film and coated with KCF3SO3-PAM hydrogel electrolyte to finally produce a flexible potassium ion microbattery.

[0048] The SEM images of the KFeMnHCF positive electrode and the PTCDI / MXene negative electrode in the embodiment are as follows Figure 2As shown in Figure 2, the PTCDI / MXene anode has a scan rate of 2 mV s -1 The CV curve is as follows Figure 3 The flexible potassium ion microbattery is shown in Figure 2. -1 The GCD curve is as follows Figure 4 As shown in the figure, the relationship between its specific capacity and Coulombic efficiency and the number of cycles is shown in Figure 5 As shown in the application of the embodiment, Figure 6 Image of a flexible potassium ion microbattery driving a single LED bulb.

[0049] To further verify the application of the flexible potassium ion microbattery obtained in the example, the sponge was immersed in 4 mg ml -1 The MXene sponge was placed in a MXene solution for several times and then dried at 40°C for 24 hours to obtain a MXene sponge with a resistance of about 100 kΩ, which was attached to a MXene electrode to obtain a MXene sponge pressure sensor. The flexible potassium ion microbattery obtained in the embodiment and the MXene sponge pressure sensor were assembled into an integrated system, such as Figure 7 The test results show that under the same stress, the relationship between the current and time of the pressure sensor driven by a single flexible potassium ion microbattery and two and three flexible potassium ion microbatteries connected in series is as follows: Figure 8 .

[0050] Example 2

[0051] A novel method for preparing a flexible potassium ion microbattery is similar to Example 1, except that in step (2), the mass ratio of PTCDI to MXene is 8:2.

[0052] Example 3

[0053] A novel method for preparing a flexible potassium ion microbattery is similar to Example 1, except that in step (2), the mass ratio of PTCDI to MXene is 7:3.

[0054] Example 4

[0055] A novel method for preparing a flexible potassium ion microbattery is similar to Example 1, except that in step (2), the mass ratio of PTCDI to MXene is 6:4.

[0056] Example 5

[0057] A novel method for preparing a flexible potassium ion microbattery is similar to Example 1, except that in step (3), the masses of acrylamide, K2S2O8 and N,N′-methylenebisacrylamide are 4 g, 40 mg and 4 mg, respectively.

[0058] Example 6

[0059] A novel method for preparing a flexible potassium ion microbattery is similar to that of Example 1, except that in step (3), the drying temperature in the oven is 80 ° C.

[0060] In the technical scheme of the present invention, although some numerical values ​​with better effects are given in the embodiments, such as the mass of PTCDI and MXene, the present invention is not limited to the mass of PTCDI and MXene given in the above embodiments. Since the mass ratio of PTCDI to MXene is 9:1-6:4, 80 mg and 20 mg as described in the embodiments can be taken, or 70 mg and 30 mg, 60 mg and 40 mg, etc. can be taken. The specific mass of PTCDI and MXene is determined according to actual needs. For example, a drying temperature with better effects is given in the embodiments, but the present invention is not limited to the drying temperature given in the above embodiments. Since the drying temperature is 70-90°C, 80°C in the embodiments can be taken, and 70°C, 90°C, etc. can be taken. The specific drying temperature is determined according to actual needs, that is, the content claimed for protection of the present invention is based on the scope recorded and explained in the claims.

[0061] It should be noted that the above-described embodiments of the present invention are only explanations and clarifications for those skilled in the art to understand the technical essence of the present invention, so the technical contents described are not intended to limit the substantial protection scope of the present invention. The substantial protection scope of the present invention shall be subject to the claims. Those skilled in the art should know that any modifications, equivalent substitutions and improvements based on the substantial spirit of the present invention shall be within the substantial protection scope of the present invention.

Claims

1. A flexible potassium-ion microbattery comprising a KFeMnHCF cathode, a PTCDI / MXene anode, and a KCF3SO3-PAM hydrogel electrolyte.

2. The flexible potassium ion microbattery according to claim 1, characterized in that: The preparation method of the KFeMnHCF positive electrode is: using K4Fe(CN)6·3H2O, FeSO4·7H2O and MnSO4·H2O as raw materials for mixed reaction to obtain a precipitate, then thoroughly washing with deionized water, drying and peeling to obtain a KFeMnHCF material, and then treating to obtain a KFeMnHCF positive electrode.

3. The flexible potassium ion microbattery according to claim 2, characterized in that: The preparation method of the KFeMnHCF positive electrode is as follows: K4Fe(CN)6·3H2O, FeSO4·7H2O and MnSO4·H2O are respectively dissolved in a saturated KCl solution, and then the FeSO4·7H2O solution and the MnSO4·H2O solution are slowly dripped into the K4Fe(CN)6·3H2O solution under magnetic stirring, the formed precipitate is centrifuged and thoroughly washed with deionized water, dried and peeled to obtain a KFeMnHCF filter cake, and the KFeMnHCF filter cake is laser engraved into an interdigitated electrode to obtain the KFeMnHCF positive electrode.

4. The flexible potassium ion microbattery according to claim 3, characterized in that: The molar ratio of K4Fe(CN)6·3H2O, FeSO4·7H2O and MnSO4·H2O is 2:1-2:6-7.

5. The flexible potassium ion microbattery according to claim 3, characterized in that: The K4Fe(CN)6·3H2O, FeSO4·7H2O and MnSO4·H2O are dissolved in saturated KCl solution respectively; the magnetic stirring temperature is 60-70°C, and the magnetic stirring time is 8-12h; the drying temperature is 60-80°C, and the drying time is 8-12h.

6. The flexible potassium ion microbattery according to claim 1, characterized in that: The preparation method of the PTCDI / MXene negative electrode is as follows: PTCDI and MXene are added into a DMF solution to form a uniform mixed solution, and then vacuum filtered and dried to obtain a PTCDI / MXene material, and the PTCDI / MXene material is laser engraved into interdigitated electrodes to obtain a PTCDI / MXene negative electrode.

7. The flexible potassium ion microbattery according to claim 6, characterized in that: The PTCDI and MXene The mass ratio is 7-9:1-3; the filter membrane used in the vacuum filtration is a 0.22 μm nylon membrane; the vacuum drying temperature is 40-45° C., and the drying time is 1-2 h.

8. The flexible potassium ion microbattery according to claim 1, characterized in that: The preparation method of the KCF3SO3-PAM hydrogel electrolyte is as follows: acrylamide, K2S2O8 and N,N′-methylenebisacrylamide are added to deionized water in sequence, and then the mixture is stirred evenly and injected into a glass model for vacuum drying, and finally the prepared hydrogel film is immersed in a KCF3SO3 aqueous solution to reach an equilibrium state.

9. The flexible potassium ion microbattery according to claim 8, characterized in that: The mass ratio of acrylamide, K2S2O8 and N, N′-methylenebisacrylamide is 3-4:0.03-0.04:0.004-0.005; the stirring time is 1-2h; the vacuum drying temperature is 70-80°C, and the time is 1-2h; the concentration of the KCF3SO3 solution is 22-25mol·L -1 .

10. The method for preparing the flexible potassium ion microbattery according to any one of claims 1 to 9, characterized in that: The KFeMnHCF cathode and PTCDI / MXene anode were transferred to a flexible substrate and coated with KCF3SO3-PAM hydrogel electrolyte to prepare a flexible potassium-ion microbattery.

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