Electrolyte for aqueous manganese ion battery and preparation method thereof

Abstract

The invention discloses an electrolyte for an aqueous manganese ion battery in the technical field of batteries. The electrolyte is composed of manganese chloride tetrahydrate, deionized water and a high-molecular polymer additive, according to the present invention, the problem of low manganese dissolution / deposition efficiency is solved, the reversibility of the manganese negative electrode during the circulation process is improved, the cycle life of the water-based manganese ion battery is prolonged, and the manganese negative electrode can be used in the water-based manganese ion battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a water-based manganese ion battery. BACKGROUND

[0002] In recent decades, lithium ion batteries have been widely used due to their excellent energy density. However, due to the safety problems brought by organic electrolyte and the high price of raw materials, it is an urgent need to find sustainable and cost-effective energy storage systems, which has stimulated great interest in water-based multi-valence ion batteries, especially those based on manganese (Mn 2+ ) electrochemistry. Manganese batteries have compelling advantages, including natural abundance, low toxicity, high theoretical capacity (976 mAh g -1 and 7250 mAh cm -3 ), and good redox potential (-1.19 V vs. SHE), making it a promising candidate for high-energy-density storage systems.

[0003] However, the development of water-based manganese ion batteries faces severe challenges. On the one hand, compared with magnesium, aluminum, and zinc ions in typical water-based metal ion battery systems, manganese ions have a larger ion size, which significantly affects the reversible insertion / extraction of manganese ions. On the other hand, the more severe challenge lies in the influence of the electrolyte environment on the reversibility of manganese deposition / dissolution. Due to the strong hydrolysis property of manganese salt, the water-based electrolyte presents a significantly strong acidity (pH<4), and the high concentration of proton environment at the electrode / electrolyte solid-liquid phase interface can severely exacerbate the hydrogen evolution reaction (HER), Mn(OH)2 deposition during manganese deposition, and disproportionation during dissolution, etc. These side reactions cause the charge transfer occurring at the negative electrode to be not effectively used for the deposition or dissolution of metallic manganese, but is largely consumed, resulting in a significant reduction in the coulombic efficiency of the manganese deposition / dissolution process (≈30%), which severely limits the service life of the battery. Developing a new type of electrolyte that can effectively suppress or alleviate these side reactions and significantly improve the coulombic efficiency of manganese deposition / dissolution is a key breakthrough for the application of water-based manganese ion batteries. SUMMARY

[0004] In view of the deficiencies in the prior art, the present application provides an electrolyte for a water-based manganese ion battery and a preparation method thereof, which solves the problem of low manganese dissolution / deposition efficiency and improves the reversibility of the manganese negative electrode during the cycling process and the cycle life of the water-based manganese ion battery.

[0005] The purpose of the present application is achieved by an electrolyte for a water-based manganese ion battery for stabilizing a manganese negative electrode, which is composed of manganese chloride tetrahydrate, deionized water, and a high molecular polymer additive. The high polymer additive is one or a mixture of several of polyacrylamide, polyvinylpyrrolidone and polyether.

[0006] Further, the polyether is polyethylene glycol.

[0007] Further, the concentration of the manganese chloride tetrahydrate is 0.5-6 mol / L, and the volume fraction of the high polymer additive is 1-10%.

[0008] A preparation method of an electrolyte, comprising the following steps: Step 1: dissolving manganese chloride tetrahydrate in deionized water to obtain a basic electrolyte; Step 2: adding a high polymer additive to the basic electrolyte, stirring until completely dissolved, and standing to obtain an electrolyte for water-based manganese ion battery for stabilizing manganese negative electrode.

[0009] A water-based manganese ion battery, comprising a positive electrode, a negative electrode and the electrolyte as claimed in any one of claims 1-3.

[0010] Further, it is a symmetric battery, comprising a manganese sheet and the electrolyte.

[0011] Further, it is a half battery, comprising a manganese sheet, a silver chloride electrode, a graphite rod and the electrolyte.

[0012] Further, it is an asymmetric battery, comprising a manganese sheet, a silver chloride electrode, a copper sheet and the electrolyte.

[0013] Further, it is a full battery, comprising a manganese negative electrode, a vanadium oxide positive electrode and the electrolyte.

[0014] Compared with the prior art, the present application has the following beneficial effects: (1) The present application uses a high polymer as an electrolyte additive, and through the coordination of the coordination groups in the high polymer with Mn 2+ , the free state manganese is prevented from participating in the disproportionation reaction, and the inherent hydrogen bond network between water molecules in the basic MnCl2 electrolyte is changed, which reduces the number of high-activity "free" water molecules released to the electrode / electrolyte interface during the Mn deposition / dissolution process, and inhibits the hydrogen evolution reaction and the corrosion reaction.

[0015] (2) The present application uses a high polymer as an electrolyte additive, and the additive molecules tend to be adsorbed on the surface of the manganese metal electrode. This adsorption layer forms a physical barrier, i.e. a high polymer film. The film blocks the direct contact of active water molecules and dissolved oxygen with the manganese surface, greatly inhibits the side reaction and reduces the loss of manganese. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only aim at the embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of the provided drawings.

[0017] Figure 1 is the Fourier infrared test (FTIR) spectrum of the electrolyte obtained in Example 1 and Example 2 and the comparative example in the present application.

[0018] Figure 2 is the linear sweep voltammetry (LSV) curve of the half-cell battery assembled by using the electrolyte obtained in Example 1 and the comparative example in the present application.

[0019] Figure 3 is the X-ray diffraction (XRD) image of the negative electrode of the Mn / / Mn symmetric battery after 10 h of cycling, which is assembled by using the electrolyte of Example 1 and the comparative example in the present application.

[0020] Figure 4 is the Cu / / Mn asymmetric battery assembled by using the electrolyte of Example 1 and the comparative example in the present application, and the current density is 180 mAcm-2. -2 Coulomb efficiency graph under super-large current density.

[0021] Figure 5 is the cycle performance curve of the full battery assembled by using the electrolyte of Example 1 and the comparative example in the present application.

[0022] Figure 6 is the cycle performance curve of the full battery assembled by using the electrolyte of Comparative Example 4 and Example 2 in the present application. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0024] As shown in the figure Example 1 A preparation method of an aqueous manganese ion battery, comprising the following steps: Step 1) Dissolve manganese chloride tetrahydrate in deionized water to obtain a basic electrolyte; Step 2) Add polyacrylamide additive to the base electrolyte, stir at a speed of 800 rpm for 1 h, stand for 2 h, to obtain an electrolyte, wherein the concentration of manganese chloride tetrahydrate is 2 mol L -1 , and the volume fraction of polyacrylamide additive is 5%; Step 3) Based on the above preparation of electrolyte, assemble a half battery.

[0025] Example 2 A preparation method of an aqueous manganese ion battery, comprising the following steps: Step 1) Dissolve manganese chloride tetrahydrate in deionized water to obtain a base electrolyte; Step 2) Add polyacrylamide additive to the base electrolyte, stir at a speed of 800 rpm for 1 h, stand for 2 h, to obtain an electrolyte, wherein the concentration of manganese chloride tetrahydrate is 2 mol L -1 , and the volume fraction of polyacrylamide additive is 10%; Step 3) Based on the above preparation of electrolyte, assemble a half battery.

[0026] Example 3 A preparation method of an aqueous manganese ion battery, comprising the following steps: Step 1) Dissolve manganese chloride tetrahydrate in deionized water to obtain a base electrolyte; Step 2) Add polyacrylamide additive to the base electrolyte, stir at a speed of 800 rpm for 1 h, stand for 2 h, to obtain an electrolyte, wherein the concentration of manganese chloride tetrahydrate is 2 mol L -1 , and the volume fraction of polyacrylamide additive is 5%; Step 3) Based on the above preparation of electrolyte, assemble a Cu / Mn asymmetric battery.

[0027] Example 4 A preparation method of an aqueous manganese ion battery, comprising the following steps: Step 1) Dissolve manganese chloride tetrahydrate in deionized water to obtain a base electrolyte; Step 2) Add polyacrylamide additive to the base electrolyte, stir at a speed of 800 rpm for 1 h, stand for 2 h, to obtain an electrolyte, wherein the concentration of manganese chloride tetrahydrate is 2 mol L -1 , and the volume fraction of polyacrylamide additive is 10%; Step 3) Based on the above preparation of electrolyte, assemble a Cu / Mn asymmetric battery.

[0028] Example 5 A preparation method of an aqueous manganese ion battery, comprising the following steps: Step 1) Dissolve manganese chloride tetrahydrate in deionized water to obtain a base electrolyte; Step 2) Add polyvinylpyrrolidone additive to the base electrolyte, stir at a speed of 800 rpm for 1 h, stand for 2 h, to obtain an electrolyte, wherein the concentration of manganese chloride tetrahydrate is 3 mol L -1 , and the volume fraction of polyvinylpyrrolidone additive is 5%; Step 3) Based on the above preparation of electrolyte, assemble Mn / / Mn symmetric battery.

[0029] Example 6 A preparation method of an aqueous manganese ion battery, comprising the following steps: Step 1) Dissolve manganese chloride tetrahydrate in deionized water to obtain a base electrolyte; Step 2) Add polyvinylpyrrolidone additive to the base electrolyte, stir at a speed of 800 rpm for 1 h, stand for 2 h, to obtain an electrolyte, wherein the concentration of manganese chloride tetrahydrate is 3 mol L -1 , and the volume fraction of polyvinylpyrrolidone additive is 10%; Step 3) Based on the above preparation of electrolyte, assemble Mn / / Mn symmetric battery.

[0030] Comparative Example Comparative Example 1 The electrolyte provided by the present comparative example is a base electrolyte obtained by dissolving manganese chloride tetrahydrate in deionized water, wherein the concentration of manganese chloride tetrahydrate is 2 mol L -1 Comparative Example 2 The electrolyte provided by the present comparative example is a base electrolyte obtained by dissolving manganese chloride tetrahydrate in deionized water, wherein the concentration of manganese chloride tetrahydrate is 3 mol L -1 Comparative Example 3 The electrolyte provided by the present comparative example is a base electrolyte obtained by dissolving manganese chloride tetrahydrate in deionized water, wherein the concentration of manganese chloride tetrahydrate is 4 mol L -1 The performance of the above-mentioned Examples 1-6 and Comparative Examples 1-3 is detected as follows, and the following conclusions are obtained.

[0031] Figure 1 is the linear sweep voltammetry (LSV) curve of the half-cell battery assembled by using the electrolyte obtained in all of Examples 1 and 2 and Comparative Example 1. It can be seen that the effect of inhibiting hydrogen gas with the electrolyte containing the high molecular additive is significantly improved.

[0032] Figure 2are the Fourier infrared test (FTIR) spectra of the electrolytes of Example 3 and Example 4 and Comparative Example 2. The distinct peaks at ~2700-3700 (Fig. a) and 1400-1800 cm -1 (Fig. b) can be observed, corresponding to O-H bending and stretching vibration modes, respectively. It can be seen that the H-O bending and H-O stretching intensities in the electrolytes of Examples are significantly reduced compared to the electrolyte of Comparative Example, indicating the disturbance of the additive to the water hydrogen bond network.

[0033] Figure 3 are the X-ray diffraction (XRD) images of the manganese negative electrodes of the Mn / / Mn symmetric cells assembled with the electrolytes of Example 5 and Comparative Example 3 after 10 h cycling. The results show that a uniform manganese deposition is obtained in the electrolyte containing the high-molecular additive, while the manganese surface has been completely changed into manganese by-products in the electrolyte of Comparative Example, greatly reducing the manganese utilization.

[0034] Figure 4 are the scanning electron microscope (SEM) images of the manganese negative electrodes of the Mn / / Mn symmetric cells assembled with the electrolytes of Example 6 and Comparative Example 3 after 10 h cycling. The results show that a uniform and smooth manganese deposition is obtained in the electrolyte containing the high-molecular additive (Fig. b), while the manganese surface has been completely changed into manganese by-products in the electrolyte of Comparative Example (Fig. a).

[0035] Figure 5 are the Cu / Mn asymmetric cell cycling performance curves of the Cu / Mn asymmetric cells assembled with the electrolytes of Example 3 and Comparative Example 2 at 180 mA cm -2 It can be seen that the overpotential of Mn is significantly reduced and the coulombic efficiency of deposition and dissolution is significantly improved in the electrolyte with the high-molecular additive even at an ultra-large current density, with a performance improvement of more than 210% compared to the comparative electrolyte.

[0036] Figure 6 are the cycling performance curves of the full cells assembled with the electrolytes of Comparative Example 4 and Example 2. It can be seen that the specific capacity in the electrolyte of Comparative Example rapidly decays to 50 mA h g -1 . In contrast, in the electrolyte of Example 2, although the electrode also undergoes an activation process in the first few cycles, it can still maintain a high discharge capacity of 100 mA h g -1 after 500 cycles.

[0037] The above description of the examples is only used to help understand the method of the present application and its core idea. It should be noted that for those skilled in the art, without departing from the principles of the present application, the present application can be improved and modified in several ways, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. An electrolyte for use in aqueous manganese-ion batteries, characterized in that, It is composed of manganese chloride tetrahydrate, deionized water, and polymer additives. The polymer additive is one or a combination of several of the following: polyacrylamide, polyvinylpyrrolidone, and polyethers.

2. The electrolyte for an aqueous manganese-ion battery according to claim 1, characterized in that, The polyether is polyethylene glycol.

3. The electrolyte for an aqueous manganese-ion battery according to claim 1 or 2, characterized in that, The concentration of manganese chloride tetrahydrate is 0.5-6 mol / L, and the volume fraction of the polymer additive is 1-10%.

4. A method for preparing the electrolyte as described in any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Dissolve manganese chloride tetrahydrate in deionized water to obtain the basic electrolyte; Step 2: Add a polymer additive to the basic electrolyte, stir until completely dissolved, and let stand to obtain an electrolyte for stabilizing the manganese negative electrode in an aqueous manganese-ion battery.

5. An aqueous manganese-ion battery, characterized in that, It includes a positive electrode, a negative electrode, and an electrolyte as described in any one of claims 1-3.

6. The aqueous manganese-ion battery according to claim 5, characterized in that, It is a symmetrical battery, comprising a manganese sheet and the electrolyte.

7. The aqueous manganese-ion battery according to claim 5, characterized in that, It is a half-cell, comprising a manganese sheet, a silver chloride electrode, a graphite rod, and the electrolyte.

8. The aqueous manganese-ion battery according to claim 5, characterized in that, It is an asymmetric battery, comprising a manganese sheet, a silver chloride electrode, a copper sheet, and the electrolyte.

9. A water-based manganese-ion battery according to claim 5, characterized in that, It is a full battery, comprising a manganese negative electrode, a vanadium oxide positive electrode, and the electrolyte.

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