In-situ surface cation-modified manganese-based aqueous potassium-ion batteries

Abstract

This invention provides an in-situ surface-modified manganese-based aqueous potassium-ion battery, which achieves in-situ surface substitution of Mn with Fe. Specifically, it involves an in-situ electrochemical conversion method, in which a manganese-based pullulan analog (KMnF) is surface-modified in a KCF3SO3 modified electrolyte, converting KMnF into KFe. x Mn 1‑x The in-situ substitution process continues until the Fe / Mn ratio at the N bond reaches a certain proportion. Specifically, it includes: using a manganese-based pullulan analog (KMnF) as the positive electrode; 3,4,9,10-tetraformamide diimide (PTCDI) as the negative electrode; preparation of the positive and negative electrodes; using a KCF3SO3-modified electrolyte containing 21 mol / L KCF3SO3 and 0.2 mol / L Fe(CF3SO3)2 aqueous solution as the electrolyte; assembly of a manganese-based aqueous potassium-ion battery; and completing the in-situ substitution of Mn with Fe on the surface through the first few charge-discharge cycles. This invention effectively alleviates the Jahn-Teller distortion and Mn dissolution in aqueous potassium-ion batteries during charge-discharge processes, enhances the structural stability of the electrodes, and thus obtains ultra-stable and high-energy-density aqueous potassium-ion batteries (APIBs).

Description

Technical Field

[0001] This invention relates to the fields of cathode materials, electrolytes, and aqueous potassium-ion batteries, and particularly to an in-situ surface-modified manganese-based aqueous potassium-ion battery. Background Technology

[0002] With the rapid increase in the number of portable electronic devices and the impetus of global power transmission and smart grids, the demand for large-scale, sustainable, environmentally friendly, and safe high-energy / power-density electrochemical energy storage devices (EESDs) is growing. In this regard, aqueous alkali metal batteries are promising storage devices because they are environmentally friendly, low-cost, and support long cycle lives. Aqueous lithium batteries have also been extensively studied and are considered promising. However, the low reserves of lithium on Earth may not be able to meet the global demand for large-scale lithium-based EESDs. Among alternative EESDs, aqueous potassium-ion batteries (APIBs) are highly attractive due to the abundant reserves of potassium on Earth, low cost, and low standard electrode potential (-2.93V relative to a conventional hydrogen electrode). Furthermore, in solvents such as propylene carbonate, with Li... + ion In comparison, K + Stokes radius of ions Smaller, which indicates that K + Ions can achieve rapid kinetics (high ion mobility and ion conductivity). Nevertheless, the development of APIBs has been greatly hampered by their low energy density and poor cycle lifetime, primarily due to the large K0. + The ionic radius can lead to significant lattice distortion and pulverization of the host electrode material during cycling. Therefore, existing APIBs technology needs improvement. Summary of the Invention

[0003] To reduce Jahn-Teller distortion and Mn dissolution in aqueous potassium-ion batteries during charge-discharge cycles, enhance electrode structural stability, and thus improve the overall stability of the aqueous potassium-ion battery, this invention provides an in-situ surface-modified manganese-based aqueous potassium-ion battery. The manganese-based aqueous potassium-ion battery is characterized in that the positive electrode of the battery undergoes in-situ surface Fe substitution of Mn, specifically through an in-situ electrochemical conversion method, i.e., surface modification of a manganese-based pullulan analog (KMnF) in a KCF3SO3 modified electrolyte, converting KMnF into KFe. x Mn 1-x F, and the in-situ substitution process continues until the Fe / Mn ratio on the N bond reaches a certain proportion.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A manganese-based aqueous potassium-ion battery, comprising:

[0006] Manganese-based pullulan analogue (KMnF) was used as the positive electrode;

[0007] 3,4,9,10-Tetracarboxydiimide (PTCDI) was used as the negative electrode;

[0008] Preparation of positive and negative electrodes;

[0009] The KCF3SO3 modified electrolyte contains 21 mol / L KCF3SO3 and 0.2 mol / L Fe(CF3SO3)2 aqueous solution as the electrolyte;

[0010] Assembly of manganese-based aqueous potassium-ion batteries;

[0011] Through the first few charge-discharge cycles, the surface Fe was substituted in situ for Mn, converting the positive electrode KMnF into KFe. x Mn 1-x F;

[0012] Furthermore, the preparation process of the manganese-based pullulan analog (KMnF) cathode material includes: dissolving 6 mmol of potassium ferrocyanide trihydrate (K4Fe(CN)6·3H2O) in 200 ml of deionized water to form solution A. Then, dissolving 6 mmol of manganese(II) sulfate monohydrate (MnSO4·H2O) and 8 g of potassium citrate in 200 ml of deionized water to form solution B. Then, at 60°C, solution B is slowly added dropwise to solution A while continuously stirring. After 12 h, the resulting mixed solution is aged at 60°C for 24 h. Then, centrifugation is performed to obtain a white precipitate, which is then washed several times with deionized water and ethanol, and finally vacuum dried at 85°C for 24 h.

[0013] Furthermore, the PTCDI was purchased from Sigma-Aldrich;

[0014] Furthermore, the positive and negative electrode preparation process includes the following steps: weighing and mixing active material (KMnF material or PTCDI material) (70%), Ketjen black (20%), and sodium carboxymethyl cellulose (10%), and then dispersing it in a mixed solution of deionized water and ethanol. The obtained slurry is then uniformly coated onto carbon fiber cloth and finally vacuum dried at 85°C for 18-36 hours.

[0015] Furthermore, the volume ratio of the deionized water and ethanol in the mixed solution is 4:1;

[0016] Furthermore, the manganese-based aqueous potassium-ion battery is a half-cell or a full-cell battery.

[0017] Furthermore, in the manganese-based aqueous potassium-ion half-cell, KMnF is used as the working electrode; Pt is used as the counter electrode; and Ag / AgCl is used as the reference electrode; wherein the loading of KMnF positive electrode active material is approximately 3 mg cm⁻¹. 2 ;

[0018] Furthermore, the manganese-based aqueous potassium-ion full cell is a button cell. Before assembling the button cell, the positive and negative electrodes undergo five charge-discharge cycles (pre-potassium treatment) in a three-electrode system; wherein the active material loading of both the KMnF positive electrode and the PTCDI negative electrode is 3 mg / cm³. 2 ;

[0019] Furthermore, the manganese-based aqueous potassium-ion full cell is a pouch cell, wherein the active material loading of both the KMnF positive electrode and the PTCDI negative electrode is 20 mg / cm³. 2 ;

[0020] The in-situ surface-modified manganese-based aqueous potassium-ion battery provided by this invention utilizes an in-situ electrochemical conversion method to modify the surface of a manganese-based pullulan analog (KMnF) in a KCF3SO3 modified electrolyte, converting KMnF into KFe. x Mn 1-x F, achieving in-situ Fe substitution of Mn on the positive electrode surface. This effectively alleviates Jahn-Teller distortion and Mn dissolution in aqueous potassium-ion batteries during charge and discharge, enhances the structural stability of the electrode, and thus obtains ultra-stable and high-energy-density aqueous potassium-ion batteries (APIBs). Therefore, the manganese-based aqueous potassium-ion half-cell or full-cell provided by this invention has the following beneficial effects:

[0021] The manganese-based aqueous potassium-ion half-cell based on the modified KMnF cathode has the following characteristics: (1) high capacity, i.e., a capacity of 300 mAh g. -1 It exhibits 160 mAh g at current density -1 (1) Discharge capacity, equivalent to 95% of the total K+ participating in the insertion / deintercalation process; (2) Long cycle life, i.e., at 2500mAh g -1 It retains 99% capacity after 100,000 cycles at current density.

[0022] Manganese-based aqueous potassium-ion full batteries have the following characteristics: (1) High energy density, reaching 92Wh / kg -1 (2) Long cycle life, at 1500mAh g -1 (2) It retains 90% of its capacity after 5000 cycles at current density; (3) It has excellent high and low temperature performance, that is, bag-type APIBs can operate stably at temperatures from -20℃ to 50℃; (4) It has high safety, that is, it can be operated safely even if 1 / 3 of the bag-type APIBs is cut. Attached Figure Description

[0023] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0024] Figure 1 The present invention provides an in-situ surface cation-modified manganese-based aqueous potassium-ion battery, comprising: a) a schematic diagram comparing the JT effect and Mn dissolution caused by the in-situ substitution of Mn by Fe in the KMnF cathode in the modified electrolyte and the absence of in-situ substitution in the conventional electrolyte; b) charge-discharge curves of the aqueous potassium-ion half-cell based on the KMnF cathode in the modified electrolyte and the conventional electrolyte after 40 cycles; and c) a graph showing the content of transition metal ions (Fe and Mn) in the KMnF cathode at different cycle numbers in the modified electrolyte.

[0025] Figure 2 Electrochemical performance diagram of the in-situ surface-modified manganese-based aqueous potassium ion half-cell provided by this invention: a) at 700 mA g -1 a) Charge / discharge curves of manganese-based aqueous potassium-ion half-cells in the 1st, 10th, and 40th cycles within a voltage range of 0V to 1.25V (relative to Ag / AgCl) at various current densities. b) Rate performance and corresponding coulombic efficiency of manganese-based aqueous potassium-ion half-cells at various current densities. c) Comparison of capacity versus current density curves of the modified KMnF cathode provided by this invention and other reported aqueous potassium-ion battery cathodes. d) Long-term cycling performance of manganese-based aqueous potassium-ion half-cells. e) Comparison of the modified KMnF cathode provided by this invention with other reported aqueous potassium-ion battery cathodes in terms of cycle life (Cyc), specific capacity (SCH / L) at high / low rates, discharge plateau (DP), capacity retention (CR), and final capacity (FC).

[0026] Figure 3 This invention provides the reaction mechanism of in-situ surface cation modification of manganese-based aqueous potassium-ion battery cathode by in-situ Fe substitution of Mn: a) in-situ XRD patterns of the KMnF electrode in the modified electrolyte during the first to fifth charge / discharge cycles; b) Raman spectra of the KMnF electrode in the modified electrolyte before and after the first cycle; c and d are STEM line scans of the electrode before and after the first cycle; e and f are HAADF-STEM images of the electrode before and after the first cycle.

[0027] Figure 4 This invention provides an elemental analysis of the Fe / Mn ratio after in-situ surface cation modification of manganese-based aqueous potassium-ion batteries, following Fe in-situ substitution of Mn: a, K2MnF and K2Fe. 0.15 Mn0.85 Density in the structural state of the F model; b, K2MnF and K2Fe 0.15 Mn 0.85 The migration energy barrier for K-ion diffusion within the lattice under the F-model structural state; c, K 2-x Fe 0.15 Mn 0.85 The lattice parameters and volume changes of F vary with the charge state x; de, the density of states (DOS) of the corresponding states are projected onto Fe and Mn; f, the contents of Mn and Fe in KMnF during the initial, 5th, 100th, and 200th cycles are determined by EDS analysis.

[0028] Figure 5 This invention provides a theoretical prediction diagram of the Mn–N bond changes during discharge of a manganese-based aqueous potassium-ion battery with in-situ surface cation modification: a and c are K2MnF and K2Fe, respectively. 0.15 Mn 0.85 The monoclinic phase of F; b and d show the changes in Mn–N bond length in the two states, respectively.

[0029] Figure 6 This invention provides the electrochemical performance of an aqueous potassium-ion full cell based on KMnF / / modified electrolyte / / PTCDI: a) rated capacity and coulombic efficiency of the full cell at various current densities within a voltage range of 0V to 2.4V. b) full cell performance at 300 to 2000 mA g. -1 Charge-discharge curves at current density; c. Button cell at 1500 mA g -1 Long-term cycling performance at current density; d. Comparison of average voltage, capacity based on total mass of two electrodes, cycle life, and energy density of button cell full cells with reported aqueous K / Na ion full cells; e. Comparison of pouch cell full cells at different temperatures (-20°C to 50°C) and 800 mA g. -1 Performance curves at current density; the inset of e shows two optical photographs of an APIB pouch cell and a cut-open APIB pouch cell, respectively.

[0030] Figure 7 This invention provides a schematic diagram of an aqueous potassium-ion full battery (button cell or pouch cell) based on KMnF / / modified electrolyte / / PTCDI for powering an LED screen. Detailed Implementation

[0031] 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.

[0032] like Figure 1 As shown, this invention provides an in-situ surface-modified manganese-based aqueous potassium-ion battery. In this manganese-based aqueous potassium-ion battery, the positive electrode is modified by in-situ surface Fe substitution of Mn. Specifically, this is achieved through an in-situ electrochemical conversion method, i.e., surface modification of a manganese-based pullulan analog (KMnF) in a KCF3SO3 modified electrolyte, converting KMnF into KFe. x Mn 1-x F, and the in-situ substitution process continues until the Fe / Mn ratio at the N bond reaches a certain proportion. The specific implementation plan is as follows:

[0033] A manganese-based aqueous potassium-ion battery, comprising:

[0034] (1) Preparation process of manganese-based pullulan analog (KMnF) as positive electrode: The preparation process of manganese-based pullulan analog (KMnF) positive electrode material includes: First, 6 mmol of potassium ferrocyanide trihydrate (K4Fe(CN)6·3H2O) is dissolved in 200 ml of deionized water to form solution A. Then, 6 mmol of manganese(II) sulfate monohydrate (MnSO4·H2O) and 8 g of potassium citrate are dissolved in 200 ml of deionized water to form solution B. Then, at 60℃, solution B is slowly added dropwise to solution A while continuously stirring. After 12 h, the resulting mixed solution is aged at 60℃ for 24 h. Then, the mixture is centrifuged to obtain a white precipitate, which is then washed several times with deionized water and ethanol, and finally dried under vacuum at 85℃ for 24 h.

[0035] (2) 3,4,9,10-Tetracarboxydiimide (PTCDI) was used as the negative electrode; PTCDI was purchased from Sigma-Aldrich.

[0036] (3) Preparation of positive and negative electrodes: Weigh out the active material (KMnF material or PTCDI material) (70%), Ketjen black (20%) and sodium carboxymethyl cellulose (10%) and mix them. Then disperse them in a mixed solution of deionized water and ethanol, wherein the volume ratio of deionized water to ethanol is 4:1. Coat the obtained slurry evenly on carbon fiber cloth and finally vacuum dry it at 85℃ for 24h.

[0037] (4) The KCF3SO3 modified electrolyte contains 21 mol / L KCF3SO3 and 0.2 mol / L Fe(CF3SO3)2 aqueous solution as electrolyte;

[0038] (5) Assembly of a manganese-based aqueous potassium-ion half-cell: KMnF was used as the working electrode; Pt was used as the counter electrode; and Ag / AgCl was used as the reference electrode; wherein the loading of KMnF positive electrode active material was approximately 3 mg cm⁻¹. 2 (Example 1)

[0039] Assembly of a manganese-based aqueous potassium-ion full cell: The full cell is a button cell. Before assembling the button cell, the positive and negative electrodes undergo five charge-discharge cycles (pre-potassium treatment) in a three-electrode system. The active material loading of both the KMnF positive electrode and the PTCDI negative electrode is 3 mg / cm³. 2 (Example 2)

[0040] Assembly of a manganese-based aqueous potassium-ion full cell: wherein the full cell is a pouch cell, and the active material loading of both the KMnF positive electrode and the PTCDI negative electrode is 20 mg / cm³. 2 (Example 3)

[0041] (6) Finally, through the previous charge-discharge cycles, the surface Fe is replaced by Mn in situ, and the positive electrode KMnF is converted into KFe. x Mn 1-x F;

[0042] like Figure 1 As shown, through an electrochemical reaction, Mn on the surface of the KMnF cathode can be dissolved in the KCF3SO3 modified electrolyte and then replaced in situ by Fe from the electrolyte, thus converting it into KFe. x Mn 1-x This in-situ substitution continues until the Fe / Mn ratio at the N-bond reaches a certain level, at which point Mn no longer dissolves, mitigating Jahn-Taller distortion and multiphase transition. Therefore, the stability of the cathode lattice structure is ensured, guaranteeing that the number of channels for potassium ion insertion remains constant after discharge. In contrast, in conventional electrolytes, Jahn-Taller distortion and Mn dissolution disrupt the lattice structure during charging, and during discharge, the vacancies left by Mn dissolution significantly reduce the number of intercalable potassium ions, leading to a sharp decrease in capacity. Figure 1 b shows the performance of the KMnF electrode in both conventional and modified electrolytes at a capacity of 300 mAh g. -1 The 40th charge / discharge curve at the current density. The observed specific capacity of the KMnF electrode in the conventional electrolyte is approximately 85 mAh g⁻¹. -1 The specific capacity in the modified electrolyte is approximately twice that of the modified electrolyte (160 mAh g). -1 ). Figure 1 As shown in Figure c, the results of Fe and Mn quantities in the original state and after 5, 10, 100, and 200 cycles indicate that the KMnF electrode only undergoes the Fe substitution of Mn in the first few cycles in the modified electrolyte. After 10 cycles, the Fe and Mn quantities in the modified electrolyte remain completely unchanged, suggesting that modification with Fe salts is crucial.

[0043] Figure 2The electrochemical performance of the aqueous potassium-ion half-cell of Example 1 is shown from 0 V to 1.25 V (relative to Ag / AgCl). Figure 2 As shown in Figure a, the charge-discharge curves of the 10th and 40th cycles completely overlap, indicating reversible and stable cycling performance. The charge-discharge curves of the first cycle differ from those of subsequent cycles, which is due to the structural adjustments and chemical composition changes of the electrode in the earlier cycles. After the 10th cycle, the KMnF electrode exhibits good performance at 700 and 7000 mA g / g. -1 It provides 149 and 95 mAh g at high current densities, respectively. -1 The reversible capacity. When the current density increases from 7000 mA g -1 Reduced to 4000, 2500, 1500 and 700 mA g -1 At that time, the capacity was restored to 95, 108, 116, 129 and 149 mAh g, respectively. -1 . Figure 2 c shows a performance comparison of the modified KMnF cathode and other reported aqueous potassium-ion battery cathodes, with the results indicating that the modified KMnF cathode provided in this invention exhibits the best performance. Due to the influence of the Fe(CF3SO3)3 modified electrolyte, at 2500 mA g... -1 The ultralong cycling stability of the modified KMnF electrode of this invention was evaluated at high current densities. The results showed that it provided a 120 mAh g⁻¹ of high current density. -1 It exhibits approximately 100% high capacity after 100,000 charge-discharge cycles, with virtually no capacity decay per cycle. Furthermore, this electrode performs well at 2500 mA g. -1 It has operated for over 400 days at current densities, far exceeding previously reported aqueous batteries. Furthermore, Figure 2 The results show that the modified KMnF electrode outperforms other reported aqueous potassium-ion battery cathodes in terms of cycle life (Cyc), specific capacity at high / low rates (SCH / L), discharge plateau (DP), capacity retention (CR), and final capacity (FC).

[0044] Figure 3 As shown, the reaction mechanism of Fe in situ substitution of Mn was studied. As is well known, Li / Na / KMnF undergoes three phase transformations from monoclinic to cubic to tetragonal. Figure 3The XRD pattern of a shows that when charged to 2.5V in the modified electrolyte, the peak corresponding to the monoclinic phase shifts slightly to the left, and new weak peaks appear at 16.5°, 23.5° and 33.6°, indicating the phase transition from the monoclinic phase to the cubic phase. However, due to the disappearance of JT, the phase transition from the cubic phase to the tetragonal phase was not observed. Figure 3 The Raman spectrum of b shows that, before discharge, the electrode is at ~2076 and ~2116 cm⁻¹. -1 Two peaks are shown, corresponding to Mn respectively. 2+ -N≡C-Fe 2+ and Mn 3+ -N≡C-Fe 2+ The vibration. When discharged to 0.01V, the Raman peaks shifted to ~2078 and ~2118 cm⁻¹, respectively. -1 Furthermore, at 2083cm -1 A shoulder peak was observed at this location, which is due to Fe 2+ -N≡C-Fe 2+ The shift in the Raman peak and the appearance of new peaks are caused by vibrations. In other words, different transition metals near the N≡C group alter the electron cloud distribution of the N≡C group, leading to changes in the group's absorption frequency. Furthermore, Figure 3 STEM line scans of c and 3d show that the Fe content in KMnF is higher than that in Mn, and this phenomenon mainly occurs on the surface of KMnF, while the composition inside is consistent with that of the original electrode. Figure 3 As shown in e and 3f, HAAF-STEM images of the KMnF electrode before and after the first cycle reveal the arrangement of K, Fe, and Mn atoms. Dark spots represent K atoms, and bright spots represent Fe and Mn atoms. The Fe and Mn pillars are displayed periodically, with the closest Mn-Mn and Fe-Fe distances being 0.715 nm, while the Mn-Fe distance is 0.506 nm. The Fe and Mn pillars (with equal contrast) are also clearly visible and stacked in the (-1-11) plane. Despite... Figure 3 Similar Fe and Mn columns were observed in the curve (obtained after the first cycle), but the Fe and Mn columns within the dashed rectangle gradually shifted upwards, likely due to Fe filling the vacancies created by Mn during charge and discharge. In summary, these results indicate that Fe present in situ in the modified electrolyte fills the vacancies created by Mn dissolution in the KMnF framework. Furthermore, the generation of vacancies due to Mn dissolution and the subsequent filling of these vacancies with Fe can also be observed in the behavior of the charge-discharge curves; that is, except for the first 10 cycles, the curves completely overlap, indicating that Mn dissolution and Fe substitution of Mn only occur in the first few charge and discharge cycles.

[0045] To explain K2Fe x Mn1-x The fundamental mechanism of K storage in the F electrode was investigated using first-principles calculations (DFT) with different JT distortions for K2MnF and K2Fe. 0.15 Mn 0.85 Density of states and K in the F electrode + Ion diffusion barrier. For example... Figure 4 As shown in a and 4b, compared to K2MnF, K2Fe 0.15 Mn 0.85 F has a relatively small band gap (1.08 eV vs. 1.58 eV) and a low K. + The ion diffusion barrier (0.30 eV vs. 0.49 eV) indicates that in-situ replacement of Mn-generated vacancies with Fe in potassium-ion batteries can improve electronic conductivity and K+. + Ion diffusion rate. Figure 4 c shows K2Fe under different charging states. 0.15 Mn 0.85 The lattice constant and volume change of the F electrode. The lattice change only resulted in a 9.8% volume shrinkage, which may reduce Jahn–Teller distortion during cycling. Figure 4 d and 4e show K2Fe under different charging states, respectively. 0.15 Mn 0.85 F, K1Fe 0.15 Mn 0.85 F, Fe 0.15 Mn 0.85 The density of states of Fe and Mn in F. And the calculated Fe... 2+ / Mn 2+ -N and Fe 2+ -C to Fe 3+ / Mn 3+ -N and Fe 3+ The energy conversion of -C is in excellent agreement with previously reported values. These atomic and electronic properties contribute to the high structural stability of the electrode and its long cycle life under high-rate conditions. Furthermore, Figure 4 EDS analysis of f showed that after 5 cycles in the modified electrolyte, the Fe to Mn ratio on the N bonds remained essentially at about 0.15:0.85, which is the same as the Fe to Mn ratio used in the calculation.

[0046] To further understand the effects of different JT distortions, first-principles calculations were performed on the structural changes of K2MnF and Fe-substituted Mn K2MnF electrodes during the potassization and depotassization processes. Figure 5 As shown in Figure a, the structure of the K2MnF electrode changes from a monoclinic phase to a cubic phase during potassium removal, and then to a tetragonal phase (Mn). 3+When the K2MnF monoclinic phase is octahedral, it undergoes JT distortion. In the K2MnF monoclinic phase, each unit cell contains 14 Mn atoms, each Mn atom is coordinated with six N atoms, and the lengths of the six Mn-N bonds are labeled d1, d2, d3, d4, d5 and d6. Figure 5 b shows that the Mn-N bonds are rapidly lengthened, further deteriorating the structure of the Mn-N6 octahedron. Figure 5 c shows the Fe-substituted Mn structure (Fe 0.15 Mn 0.85 Similar to the Mn[Fe(CN)6] structure, each Mn atom is coordinated to six N atoms; however, first-principles calculations show that the value of each Mn–N bond varies very little. This result is consistent with in-situ XRD results, indicating that the cycling stability of KMnF with Fe in-situ Mn substitution is much better than that of KMnF.

[0047] Electrochemical performance of aqueous potassium-ion full cells based on KMnF / / modified electrolyte / / PTCDI, such as Figure 6 As shown in a, the KMnF / / PTCDI full cell at 300, 800, 1500, and 2000 mA g -1 It exhibits excellent rate performance at various current densities, and offers 75, 69, 59 and 56 mAh g⁻¹ respectively. -1 The reversible capacity (based on the effective mass of the positive and negative electrodes), and when the current density recovers to 300 mA g -1 At that time, the discharge capacity recovered to 75mAh g. -1 The charge-discharge curve of the full battery is as follows: Figure 5 As shown in b, at 300mA g -1 The discharge plateau was 1.32V. Figure 6 As shown in c, the full cell operates at 800 mA g. -1 At a current density of 10000 cycles, it exhibits excellent cycle stability and 82.6% capacity retention, with a coulombic efficiency of approximately 100%. Figure 5 As shown in Figure d, the performance of the aqueous potassium-ion battery based on Fe in situ substitution of Mn provided by the present invention and the aqueous potassium / sodium-ion battery were compared. The results show that the aqueous potassium-ion battery provided by the present invention has the best energy density and cycle stability, and its performance is far superior to that of the reported aqueous potassium / sodium-ion batteries. Figure 6 As shown in Figure e, the pouch-type aqueous potassium-ion full battery provided by this invention can operate over a wide temperature range (-20°C to 50°C) and exhibits excellent high and low temperature performance. When the temperature drops from 25°C to -20°C, the pouch battery maintains an 800 mA g-force. -1It can still retain 78% of its capacity. In addition, when 1 / 3 of the pouch cell is cut off, it can still continue to work safely with 64% of its original capacity, demonstrating its high safety. Figure 7 As shown, two button batteries or pouch-type aqueous potassium-ion batteries can power the LED screen.

[0048] In summary, the in-situ surface-modified manganese-based aqueous potassium-ion battery provided by this invention utilizes an in-situ electrochemical conversion method to modify the surface of a manganese-based pullulan analog (KMnF) in a KCF3SO3 modified electrolyte, converting KMnF into KFe. x Mn 1-x Fe is used to replace Mn in situ on the cathode surface. This effectively alleviates the Jahn-Teller distortion and Mn dissolution in aqueous potassium-ion batteries during charge and discharge, and enhances the structural stability of the electrode, thereby obtaining ultra-stable and high-energy-density aqueous potassium-ion batteries (APIBs).

[0049] The above description is only 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 protection scope of the present invention.

Claims

1. A method for preparing an in-situ surface-modified manganese-based aqueous potassium-ion battery, characterized in that: The positive electrode of the manganese-based aqueous potassium-ion battery is characterized by in-situ Fe substitution of Mn on its surface. Specifically, this is achieved through an in-situ electrochemical conversion method, namely, surface modification of the manganese-based pullulan analog KMnF in a KCF3SO3 modified electrolyte, converting KMnF into KFexMn1-xF. This in-situ substitution process continues until the Fe / Mn ratio at the N-bonds reaches a certain proportion. The manganese-based aqueous potassium-ion battery comprises: The manganese-based pullulan analog KMnF was used as the positive electrode; 3,4,9,10-Tetracarboxydiimide (PTCDI) was used as the negative electrode; The KCF3SO3 modified electrolyte contains 21 mol / L KCF3SO3 and 0.2 mol / L Fe(CF3SO3)2 aqueous solution as the electrolyte; Through the first few charge-discharge cycles, the surface Fe was substituted in situ for Mn, converting the positive electrode KMnF into KFe. x Mn 1-x F.

2. The method for preparing a manganese-based aqueous potassium-ion battery according to claim 1, characterized in that: The preparation process of the manganese-based pullulan analog KMnF cathode material includes: dissolving 6 mmol of potassium ferrocyanide trihydrate (K4Fe(CN)6·3H2O) in 200 ml of deionized water to form solution A; then, dissolving 6 mmol of manganese(II) sulfate monohydrate (MnSO4·H2O) and 8 g of potassium citrate in 200 ml of deionized water to form solution B; then, at a temperature of 60°C, slowly adding solution B dropwise to solution A while continuously stirring. After 12 hours, the resulting mixed solution was aged at 60°C for 24 hours; then centrifuged to obtain a white precipitate, which was then washed several times with deionized water and ethanol, and finally vacuum dried at 85°C for 24 hours.

3. The method for preparing a manganese-based aqueous potassium-ion battery according to claim 1, characterized in that: The positive and negative electrode preparation process includes the following steps: weighing 70% KMnF material or PTCDI material, 20% Ketjen black and 10% sodium carboxymethyl cellulose and mixing them, then dispersing them in a mixed solution of deionized water and ethanol; uniformly coating the obtained slurry onto carbon fiber cloth, and finally vacuum drying at 85°C for 18-36 hours.

4. The method for preparing a manganese-based aqueous potassium-ion battery according to claim 3, characterized in that: The volume ratio of the deionized water and ethanol in the mixed solution is 4:

1.

5. The method for preparing a manganese-based aqueous potassium-ion battery according to claim 1, characterized in that: The manganese-based aqueous potassium-ion battery is either a half-cell or a full-cell battery.

6. The method for preparing a manganese-based aqueous potassium-ion battery according to claim 5, characterized in that: The manganese-based aqueous potassium-ion half-cell uses KMnF as the working electrode, Pt as the counter electrode, and Ag / AgCl as the reference electrode; wherein the loading of KMnF positive electrode active material is 3 mg cm⁻¹. -2 .

7. The method for preparing a manganese-based aqueous potassium-ion battery according to claim 5, characterized in that: The manganese-based aqueous potassium-ion full cell is a button cell. Before assembling the button cell, the positive and negative electrodes are subjected to five charge-discharge cycles in a three-electrode system. The active material loading of both the KMnF positive electrode and the PTCDI negative electrode is 3 mg / cm³. -2 .

8. The method for preparing a manganese-based aqueous potassium-ion battery according to claim 5, characterized in that: The manganese-based aqueous potassium-ion full cell is a pouch cell, wherein the active material loading of both the KMnF positive electrode and the PTCDI negative electrode is 20 mg / cm³. -2 .

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