Preparation method of high-reversibility manganese metal negative electrode and application thereof in aqueous batteries

Abstract

The application discloses a preparation method of a high-reversibility manganese metal negative electrode and application of the manganese metal negative electrode in a water-based battery, and belongs to the technical field of electrochemical energy storage materials and devices, and comprises the following steps: a metal manganese base is immersed into an organic acid solution to react, a layer of metal-organic acid salt protective layer is generated in situ on the surface of the manganese base, and a manganese metal negative electrode is obtained; wherein the organic acid is a dicarboxylic acid containing two carboxyl groups and is at least one selected from oxalic acid, malic acid and tartaric acid. Through the strong coordination effect of the multiple carboxyl groups on the manganese surface, a dense and ion-conductive interface layer is constructed, and the disorderly dissolution of manganese ions and side reactions are effectively inhibited. The interface layer can guide the ordered transmission and uniform deposition of manganese ions, significantly reduce the charge transfer impedance of the electrode / electrolyte interface, reduce the charge / discharge voltage hysteresis, and thus improve the reversibility and cycle stability of manganese deposition / dissolution.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage materials and devices, specifically relating to a method for preparing a highly reversible manganese metal anode and its application in aqueous batteries. Background Technology

[0002] Aqueous manganese-ion batteries are considered a highly promising large-scale energy storage technology due to their high safety, low cost, and environmental friendliness. Metallic manganese, with its high theoretical capacity (976 mAh g⁻¹), is a key factor in this technology. -1 and 7250 mAh cm -3 With its excellent redox potential (-1.19 V vs. SHE), manganese is an ideal anode material for aqueous manganese-ion batteries. However, the practical application of this system faces a fundamental challenge: severe corrosion caused by the extremely poor thermodynamic stability of metallic manganese in aqueous electrolytes.

[0003] Compared to the widely studied aqueous zinc-ion batteries, manganese metal anodes face more severe electrochemical reversibility challenges in aqueous electrolytes. The chemical properties of manganese make it difficult to achieve a stable and reversible deposition / dissolution process in aqueous environments, specifically manifested in: (1) severe spontaneous hydrogen evolution and other side reactions continuously consume active materials, resulting in irreversible capacity loss and low coulombic efficiency; (2) difficulty in forming a stable solid electrolyte interface (SEI) with ion conduction capability, making it difficult to control the deposition behavior of manganese ions, easily forming uneven deposition or even dendrites, further reducing reaction reversibility; (3) the continuous accumulation of irreversible corrosion products (such as manganese hydroxide), damaging the integrity of the electrode structure, and aggravating capacity decay and cycle degradation. The above problems together result in the cycle life and reversibility of manganese anodes falling far short of the requirements for practical applications.

[0004] In existing technologies, strategies for improving metal anodes mostly focus on suppressing dendrite growth, such as constructing a three-dimensional conductive framework to reduce local current density. However, for manganese anodes, increasing the surface area may exacerbate side reactions, thereby impairing their reversibility. Some studies have attempted to introduce additives (such as polymers and corrosion inhibitors) into the electrolyte to adjust the electrode / electrolyte interface, but this method involves overall adjustment of the electrolyte system, with limited effectiveness and potential cost and compatibility issues. Furthermore, while constructing artificial protective layers to isolate the electrode from the electrolyte has been widely explored, it often faces challenges such as weak interfacial bonding, insufficient long-term stability, and complex preparation processes, making it difficult to achieve highly reversible manganese deposition / dissolution while maintaining ion transport.

[0005] Therefore, there is still a lack of a method to directly construct an interface layer on the surface of manganese metal that combines ion selectivity, structural compactness and electrochemical stability, thereby fundamentally improving the reversibility of manganese anode reaction and promoting the practical application of aqueous manganese-ion batteries. Summary of the Invention

[0006] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly describe some preferred embodiments.

[0007] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0008] Therefore, the object of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a highly reversible manganese metal anode, comprising,

[0009] The manganese metal substrate is immersed in an organic acid solution for reaction, and a metal-organic acid salt protective layer is generated in situ on the surface of the manganese substrate to obtain a manganese metal anode;

[0010] The organic acid is a dicarboxylic acid containing two carboxyl groups, selected from at least one of oxalic acid, malic acid, and tartaric acid.

[0011] In a preferred embodiment of the method described in this invention, the concentration of the organic acid solution is 0.01~0.5 mol / L.

[0012] In a preferred embodiment of the method described in this invention, the reaction time is 1 min to 1 h.

[0013] Another objective of this invention is to overcome the shortcomings of the prior art and provide a manganese metal anode.

[0014] Another objective of this invention is to overcome the shortcomings of the prior art and provide an application of a manganese metal anode in the preparation of an aqueous manganese-ion battery.

[0015] In a preferred embodiment of the application described in this invention, the aqueous manganese-ion battery includes a beaker battery.

[0016] As a preferred embodiment of the application described in this invention, the beaker battery includes an asymmetric battery, a symmetric battery, and a full battery.

[0017] In a preferred embodiment of the application described in this invention, the asymmetric battery is composed of a manganese sheet, a silver chloride electrode, a copper sheet, and a 3 M manganese chloride aqueous solution electrolyte.

[0018] In a preferred embodiment of the application described in this invention, the symmetrical battery is composed of a manganese metal negative electrode and a 3 M manganese chloride aqueous solution electrolyte.

[0019] In a preferred embodiment of the application described in this invention, the full battery is composed of a manganese metal negative electrode, a vanadium oxide positive electrode, and a manganese chloride electrolyte.

[0020] Beneficial effects of this invention:

[0021] (1) This invention proposes a direct interface control strategy to improve the reversibility of manganese anode deposition / dissolution: This invention proposes and verifies that dicarboxylic acids can be used as direct modifiers for manganese anodes; through the strong coordination of their polycarboxyl groups with the manganese surface, a dense, ion-conducting metal-organic acid salt interface layer is constructed in situ. Organic acid salts can usually effectively isolate the direct contact between the electrode and the electrolyte, thereby suppressing side reactions. However, organic components usually have low ionic conductivity, which will increase the charge transfer impedance and increase the voltage polarization during charging and discharging. This protective layer not only effectively isolates the contact between the electrolyte and the manganese substrate, but also significantly reduces the interfacial charge transfer impedance (Rct), which is manifested as a significant reduction in the charging and discharging voltage hysteresis, achieving synergistic optimization of interfacial kinetics and thermodynamic stability. This interface layer can not only effectively suppress the disordered dissolution of manganese ions and the occurrence of side reactions, but also guide the orderly transport and uniform deposition of manganese ions at the electrode / electrolyte interface, thereby significantly improving the reversibility of manganese deposition / dissolution and cycle stability.

[0022] (2) Improved intrinsic interfacial stability: The in-situ generated metal-organic acid salt layer exhibits excellent chemical stability and a dense structure. This interfacial layer has excellent lattice matching with the manganese matrix, providing a low-barrier transport channel for manganese ions. It can effectively shield the effect of electric field inhomogeneity, guide the orderly transport and uniform nucleation of manganese ions, fundamentally suppress the growth of manganese dendrites, and thus significantly improve the coulombic efficiency.

[0023] (3) Improved cycle performance of manganese-based batteries: Significantly improved cycle performance and coulombic efficiency of aqueous batteries based on manganese anodes; Experiments show that the manganese anode treated by this method exhibits excellent cycle stability and high coulombic efficiency in both symmetrical and full-cell batteries. In particular, the modified anode can still maintain stable deposition / stripping behavior under high current density, proving that the interface layer has excellent structural stability and electrochemical reversibility, providing a reliable route for the preparation of highly reversible manganese metal anodes.

[0024] (4) The process has industrialization advantages: The preparation method is a one-step room temperature soaking method, which does not require complex equipment, harsh conditions or expensive raw materials. The process is extremely simple, energy consumption is low, and it is compatible with existing electrode production processes, and has great potential for large-scale application. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0026] Figure 1 A Cu / / Mn asymmetric cell assembled from the manganese negative electrode treated in Example 1 of this invention and the negative electrode of Comparative Example 1 was tested at 180 mA cm⁻¹. -2 Comparison of coulombic efficiency under ultra-high current density.

[0027] Figure 2 The images show a comparison of the manganese negative electrode surface using scanning electron microscopy (SEM) of Embodiment 2, Comparative Example 1, and Comparative Example 2 of the present invention.

[0028] Figure 3 The electrochemical impedance spectroscopy (EIS) spectra of the symmetrical cells assembled using the negative electrodes of Example 3 and Comparative Example 1 after cycling for 1 h and 10 h, respectively.

[0029] Figure 4 This is a comparison chart of the cycle performance of a symmetrical battery assembled with the manganese anode treated in Example 2 and the anode of Comparative Example 1.

[0030] Figure 5 This is a comparison chart of the long-cycle performance and coulombic efficiency of full cells assembled using the negative electrodes of Example 2 and Comparative Example 1 (with vanadium oxide as the positive electrode).

[0031] Figure 6 The graph shows a comparison of the cycle performance of symmetrical batteries assembled using the negative electrodes of Examples 1, 2, 3, Comparative Examples 1 and 2. Detailed Implementation

[0032] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification. The raw materials used in the present invention are all commercially available products.

[0033] Example 1

[0034] (1) Polish the commercial manganese sheet with sandpaper, then ultrasonically clean it with ethanol and deionized water in sequence and dry it.

[0035] (2) Prepare a 0.5 mol / L malic acid aqueous solution.

[0036] (3) Immerse the cleaned manganese sheet completely in the malic acid solution and let it stand at room temperature for 30 minutes.

[0037] (4) After the reaction is complete, the manganese sheet is removed, rinsed thoroughly with deionized water, and then dried in a vacuum oven at 60°C for 12 hours to obtain a modified negative electrode with a manganese malate protective layer on the surface.

[0038] Test method: An assembly consisting of a manganese sheet with a manganese malate protective layer as the counter electrode, a silver chloride electrode as the reference electrode, a copper sheet as the working electrode, and a 3 M manganese chloride aqueous solution as the electrolyte was tested at 180 mA cm⁻¹. -2Assemble a Cu / / Mn asymmetric cell under the specified conditions and test the cell's coulombic efficiency.

[0039] Using 3 M manganese chloride as the electrolyte, two manganese plates with a manganese malate protective layer were used at 1 mA cm⁻¹. -2 and 0.5mAh cm -2 Assemble Mn / / Mn symmetric cells under the given conditions.

[0040] Example 2

[0041] (1) Polish the commercial manganese sheet with sandpaper, then ultrasonically clean it with ethanol and deionized water in sequence and dry it.

[0042] (2) Prepare a 0.1 mol / L oxalic acid aqueous solution.

[0043] (3) Immerse the cleaned manganese sheet completely in the oxalic acid solution and let it stand at room temperature for 30 minutes.

[0044] (4) After the reaction is complete, the manganese sheet is removed, rinsed thoroughly with deionized water, and then dried in a vacuum oven at 60 °C for 12 hours to obtain a modified negative electrode with a manganese oxalate protective layer on the surface.

[0045] Test method: Using 3 M manganese chloride as the electrolyte, two manganese plates with a manganese oxalate protective layer were used at 1 mA cm⁻¹. -2 and 0.5 mAh cm -2 Assemble Mn / / Mn symmetric cells under the given conditions.

[0046] Using vanadium oxide as the positive electrode, 3 M manganese chloride as the electrolyte, and a manganese sheet with a manganese oxalate protective layer as the negative electrode, in 1 Ag... -1 Assemble all batteries under the conditions.

[0047] Example 3

[0048] (1) Polish the commercial manganese sheet with sandpaper, then ultrasonically clean it with ethanol and deionized water in sequence and dry it.

[0049] (2) Prepare a 0.01 mol / L tartaric acid aqueous solution.

[0050] (3) Immerse the cleaned manganese sheet completely in tartaric acid solution and let it stand at room temperature for 30 minutes.

[0051] (4) After the reaction is complete, the manganese sheet is taken out, rinsed thoroughly with deionized water, and then dried in a vacuum oven at 60°C for 12 hours to obtain a modified negative electrode with a manganese tartrate protective layer on the surface.

[0052] Test method: Using 3 M manganese chloride as the electrolyte, two manganese plates with a manganese tartrate protective layer were used at 1 mA cm⁻¹. -2and 0.5 mAh cm -2 Assemble Mn / / Mn symmetric cells under the given conditions.

[0053] Comparative Example 1

[0054] Commercially available manganese sheets without any processing were used as the negative electrode for comparison.

[0055] Test method: An assembly consisting of a manganese sheet as the counter electrode, a silver chloride electrode as the reference electrode, a copper sheet as the working electrode, and a 3 M manganese chloride aqueous solution as the electrolyte was tested at 180 mA cm⁻¹. -2 Assemble a Cu / / Mn asymmetric cell under the specified conditions and test the cell coulombic efficiency.

[0056] Using 3 M manganese chloride as the electrolyte, two original manganese plates were used at 1 mA cm⁻¹ -2 and 0.5 mAh cm -2 Assemble Mn / / Mn symmetric cells under the given conditions.

[0057] Using vanadium oxide as the positive electrode, 3 M manganese chloride as the electrolyte, and the original manganese sheet as the negative electrode, at 1 A g -1 Assemble all batteries under the conditions.

[0058] Comparative Example 2

[0059] (1) Polish the commercial manganese sheet with sandpaper, then ultrasonically clean it with ethanol and deionized water in sequence and dry it.

[0060] (2) Prepare a 0.1 mol / L oxalic acid aqueous solution.

[0061] (3) Immerse the three cleaned manganese sheets in oxalic acid solution and let them stand at room temperature for less than 1 min (30 s), 50 min and more than 60 min (70 min) respectively.

[0062] (4) After the reaction is complete, the manganese sheet is removed, rinsed thoroughly with deionized water, and then dried in a vacuum oven at 60 °C for 12 hours to obtain three modified negative electrodes with a manganese oxalate protective layer on the surface.

[0063] Test method: The surface morphology of manganese flakes treated with different soaking times was observed by scanning electron microscopy (SEM).

[0064] Using 3 M manganese chloride as the electrolyte, two manganese plates with a manganese oxalate protective layer were used at 1 mA cm⁻¹. -2 and 0.5 mAhcm -2 Assemble Mn / / Mn symmetric cells under the given conditions.

[0065] Performance characterization results

[0066] 1. Figure 1This is a comparison of the coulombic efficiencies of the Cu / / Mn asymmetric cells in Example 1 and Comparative Example 1. It can be seen that at 180 mA cm⁻¹... -2 Under ultra-high current density, the overpotential of Mn in the manganese anode with a malic acid protective layer is significantly reduced and the coulombic efficiency of deposition and dissolution is significantly improved, with a performance improvement of over 150% compared to the control anode.

[0067] 2. Figure 2 The scanning electron microscope results for Example 2, Comparative Example 1, and Comparative Example 2 are shown below. Figure 2 Comparative Example 1-a shows a scanning electron microscope image of the original manganese sheet surface, which can be seen to show that its surface is relatively uneven with obvious particles. Figure 2 Comparative Example 2-b is a scanning electron microscope image of the manganese sheet in Comparative Example 2 when the immersion time is less than 1 min. It can be seen that the manganese surface is not completely covered. Figure 2 Example 2-c is a scanning electron microscope image of a manganese sheet soaked in manganese oxalate for 30 minutes in Example 2. It can be seen that the surface is covered with a uniform and dense layer of manganese oxalate without cracks or pores. The dense structure guides the orderly transport of manganese ions, thereby ensuring high coulombic efficiency and structural stability. Figure 2 Comparative Example 2-d is a scanning electron microscope image of the manganese sheet in Comparative Example 2 after soaking for 50 min. It can be seen that slight cracks appeared on the manganese surface. Figure 2 Comparative Example 2-e shows a scanning electron microscope image of the manganese sheet from Comparative Example 2 after immersion for more than 60 minutes. It can be seen that the manganese surface particles became larger, the surface became rougher, and cracks appeared. These cracks disrupted the density of the protective layer, leading to complex ion transport paths deep within the cracks and increasing the resistance to interfacial ion diffusion.

[0068] 3. Figure 3 The EIS curves of the Mn / / Mn symmetric cells assembled from the manganese sheets of Example 3 and Comparative Example 1 after 1 h and 10 h of cycling are shown. The results show that the charge transfer resistance (Rct) of Example 3 is significantly lower than that of Comparative Example 1, confirming the excellent ionic conductivity of the in-situ generated organic acid manganese layer. The charge transfer resistance Rct of the negative electrode in Example 3 is reduced, indicating smoother charge transfer, and the curve of Example 3 is flatter in the low-frequency region, suggesting that the presence of the organic acid salt promotes ion diffusion within the electrode. After 10 cycles, the electrochemical kinetic performance is still significantly better than that of bare Mn.

[0069] 4. Figure 4This is a comparison of the performance of the symmetrical cells using the negative electrode of Example 2 and the negative electrode of Comparative Example 1. The symmetrical cell using the negative electrode of Comparative Example 1 failed after approximately 50 hours. The symmetrical cell using the negative electrode of Example 2 cycled stably for over 150 hours, with minimal voltage hysteresis and stable polarization voltage during cycling, demonstrating the effectiveness of the dicarboxylic acid. This directly reflects the improved kinetics of the manganese deposition / stripping reaction and the effective suppression of interfacial side reactions.

[0070] 5. Figure 5 This is a comparison chart of the full-cell performance of the negative electrode from Example 2 and the negative electrode from Comparative Example 1. The full-cell using the negative electrode from Comparative Example 1 had an initial capacity of 110 mAh / g, which decreased to 80 mAh / g after 300 cycles. The full-cell using the negative electrode from Example 2 had an initial capacity of 140 mAh / g, which remained at 105 mAh / g after 700 cycles, and the coulombic efficiency remained above 99.5% throughout.

[0071] 6. Figure 6 This is a comparison of the initial stage voltage-time curves of Mn / / Mn symmetric batteries prepared in different embodiments and comparative examples of the present invention during constant current cycling tests, specifically demonstrating the voltage hysteresis behavior in the first 10 charge-discharge cycles.

[0072] like Figure 6 As shown, the voltage hysteresis windows of Examples 1 (malic acid modification), 2 (oxalic acid modification), and 3 (tartaric acid modification) are all significantly smaller than those of Comparative Example 1 (unmodified). This indicates that the interface layer formed after treatment with the organic acid solution of this invention can effectively reduce charge transfer impedance, promote uniform nucleation and deposition of manganese ions, and inhibit dendrite growth and side reactions. In Comparative Example 2 (immersion time less than 1 minute), due to the extremely low coverage of the protective layer, the electrolyte can still contact the manganese matrix over a large area. This "dot-like" coverage cannot form an effective physical barrier, and side reactions (such as corrosion and hydrogen evolution) still occur frequently. At this time, the interface has not been substantially improved, the charge transfer impedance remains at a high level, and the polarization voltage of the battery cannot be effectively reduced. In Comparative Example 2 (immersion time greater than 1 hour), the cracked structure destroys the physical barrier function of the interface layer, causing the electrolyte to penetrate through the crack and undergo continuous side reactions with the manganese matrix. At the same time, the local current density at the crack is concentrated, inducing uneven deposition of manganese ions at the defect. This not only exacerbates interfacial polarization (manifested as increased charge / discharge voltage hysteresis), but ultimately leads to a decrease in the reversibility and cycle stability of manganese deposition / dissolution.

[0073] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for preparing a highly reversible manganese metal anode, characterized in that: include, The manganese metal substrate is immersed in an organic acid solution for reaction, and a metal-organic acid salt protective layer is generated in situ on the surface of the manganese substrate to obtain a manganese metal anode; The organic acid is a dicarboxylic acid containing two carboxyl groups, selected from at least one of oxalic acid, malic acid, and tartaric acid.

2. The method as described in claim 1, characterized in that: The concentration of the organic acid solution is 0.01~0.5 mol / L.

3. The method as described in claim 1 or 2, characterized in that: The reaction time is 1 min to 1 h.

4. The manganese metal anode prepared by the method according to any one of claims 1 to 3.

5. The application of the manganese metal anode according to claim 4 in the preparation of aqueous manganese-ion batteries.

6. The application as described in claim 5, characterized in that: The aqueous manganese-ion battery includes a beaker battery.

7. The application as described in claim 6, characterized in that: The beaker battery includes asymmetric batteries, symmetric batteries, and full batteries.

8. The application as described in claim 7, characterized in that: The asymmetric battery is composed of a manganese sheet, a silver chloride electrode, a copper sheet, and a 3 M manganese chloride aqueous solution electrolyte.

9. The application as described in claim 7, characterized in that: The symmetrical battery consists of a manganese metal negative electrode and a 3 M manganese chloride aqueous solution electrolyte.

10. The application as described in claim 7, characterized in that: The full battery consists of a manganese metal negative electrode, a vanadium oxide positive electrode, and a manganese chloride electrolyte.

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