Iron negative electrode material with excellent performance, ultrafast low-temperature synthesis method and application thereof

Abstract

The application provides an iron negative electrode material with excellent performance, which comprises an iron base, and a manganese and sulfur co-doped hydroxyl iron oxide material is generated in situ on the surface of the iron base through solution immersion; the solution comprises water, a high-valence manganese compound and a thiosulfate. The iron negative electrode material has the characteristics of good electronic conductivity, high area capacity, excellent rate performance, stable cycle life and the like. The water-based alkaline battery based on the iron negative electrode material has high energy density and long cycle life.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemical energy storage materials, and more particularly to an iron negative electrode material with excellent performance and a super-fast low-temperature synthesis method and application thereof. BACKGROUND

[0002] Optimizing energy structure and developing efficient low-carbon clean energy are important directions for sustainable development in today's world. As a representative electrochemical energy and storage device, rechargeable batteries have important practical significance for reducing fossil fuel consumption and reducing environmental pollution. In recent years, lithium-ion batteries with high specific energy and long cycle life have been continuously expanded in production under the driving of market demand for electric vehicles. However, the pursuit of higher energy density and lower cost by electric vehicles has triggered research on alternative technologies for the post-lithium-ion era. At the same time, the scarcity, high cost and safety problems of lithium, the core element of lithium-ion batteries, have greatly limited their practicality. Therefore, it is extremely urgent to explore energy storage systems with high theoretical energy density, inherent safety and environmental friendliness. It is urgent to develop new energy storage devices to replace lithium-ion batteries.

[0003] Iron-based aqueous alkaline batteries have been developed for more than a hundred years. Compared with the current commercial lead-acid batteries and lithium-ion batteries, their development is relatively lagging behind. However, with the advent of the post-lithium era, in the last decade, iron-based aqueous batteries have attracted widespread attention from researchers due to their low cost, ease of assembly, environmental friendliness and other advantages. Most current research focuses on positive electrode materials and has made practical progress. However, the performance of iron negative electrode materials lags far behind that of the positive electrode, severely restricting the application and development of iron-based aqueous alkaline batteries. Iron negative electrode mainly stores energy through redox reactions during charging and discharging. Due to the lack of suitable iron negative electrode materials, the process has slow reaction kinetics and low charge transfer capacity, resulting in low capacity and rate performance of the battery. Currently, the modification of iron negative electrode mainly involves the composite with carbon materials, morphology engineering and vacancy defects, etc. For example, S-doped Fe2O3 nanowire array negative electrode materials are synthesized on carbon cloth through hydrothermal and high-temperature sulfidation; carbon-coated Fe3O4 negative electrodes are prepared by hydrothermal and high-temperature carbonization; FeP negative electrodes are obtained by hydrothermal and phosphidation treatment. Although the above modifications can improve the performance of the iron negative electrode, the existing iron-based materials have defects and deficiencies such as complicated synthesis process, high energy consumption, and inability to be prepared in large areas. Therefore, it is necessary to develop a fast and simple preparation method to obtain iron negative electrode materials with excellent performance and solve the practical application problems of iron-based aqueous batteries. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the defects and deficiencies of the existing iron-based material synthesis process, such as complicated process, high energy consumption and inability to prepare in large area, and to provide an iron negative electrode material with high capacity, good rate performance and cycle stability and a synthesis method of the iron negative electrode material with excellent performance synthesized at ultrafast low temperature.

[0005] The above-mentioned object of the present application is achieved by the following technical solutions.

[0006] An iron negative electrode material with excellent performance comprises an iron substrate, and a manganese and sulfur co-doped iron oxyhydroxide material is generated in situ on the surface of the iron substrate by solution immersion; the solution comprises water, a high-valence manganese compound and a thiosulfate.

[0007] Furthermore, the iron oxyhydroxide is formed by nanosheets with a size of 10-100 nm, and the nanosheets form a nano-cluster structure.

[0008] Furthermore, in the solution, the molar ratio of the high-valence manganese compound to the thiosulfate is 5-10:1. The high-valence manganese compound needs to be in a sufficient amount to react with the iron substrate, and a small amount of thiosulfate provides a weak alkaline environment for the reaction.

[0009] Furthermore, in the solution, the concentrations of the high-valence manganese compound and the thiosulfate are 0.01-0.3 mol / L and 0.001-0.05 mol / L, respectively. The concentrations of the high-valence manganese compound and the thiosulfate cannot be too high or too low. If the concentrations are too high, the reaction rate is too fast, the corrosion reaction is accelerated, the iron oxyhydroxide cannot grow in situ on the surface of the iron substrate, and a large amount of the iron oxyhydroxide is precipitated at the bottom of the solution; if the concentrations are too low, the reaction is affected and the reaction is slow, resulting in incomplete reaction.

[0010] Furthermore, the high-valence manganese compound is selected from one or both of potassium permanganate and potassium manganate.

[0011] Furthermore, the thiosulfate is selected from one or more of potassium thiosulfate, ammonium thiosulfate, sodium thiosulfate, lithium thiosulfate and calcium thiosulfate.

[0012] Furthermore, the immersion time is 3-30 min, the temperature of the immersion solution is 25-40 DEG C, and the pH value is 7.01-9.

[0013] The ultrafast low-temperature synthesis method of the iron negative electrode material with excellent performance comprises the following steps.

[0014] S1. Iron substrate cleaning: commercially available iron materials are sequentially cleaned with hydrochloric acid, acetone, deionized water and ethanol to remove surface impurities and oxide layers and obtain clean iron substrates;

[0015] S2. Synthesis of iron negative electrode material at low temperature: immerse the clean iron substrate obtained in S1 in a solution containing a high-valence manganese compound and a thiosulfate salt for a certain time to obtain an iron negative electrode material, and then take out the iron negative electrode material, sequentially clean it with deionized water and an ethanol solution, and dry it; the high-valence manganese compound is selected from one or both of potassium permanganate and potassium manganate, and the concentration is 0.01-0.3 mol / L; the thiosulfate salt is selected from one or more of potassium thiosulfate, ammonium thiosulfate, sodium thiosulfate, lithium thiosulfate, and calcium thiosulfate, and the concentration is 0.001-0.05 mol / L; and the molar ratio of the high-valence manganese compound to the thiosulfate salt is 5-10:1.

[0016] Further, the reaction time in S2 is 3-30 min, the reaction temperature is 25-40℃, the reaction pH value is 7.01-9, and the drying temperature is 60-70℃; and the cleaning time of the iron substrate in different washing solutions in S1 is 5-30 min, wherein the concentration of hydrochloric acid is 0.5-3 mol / L.

[0017] Under the condition of adding potassium permanganate in the application, the chemical reactions occurring in the synthesis process are as follows:

[0018] 4Mn 7+ +4Fe+4OH - →4Mn 4+ +4Fe 2+ +O2+2H2O

[0019] 4Fe 2+ +O2+2H2O→4Fe 3+ +4OH -

[0020] Mn 4+ +2Fe 3+ +10OH - →Mn-2FeOOH+4H2O

[0021] Under the condition of adding potassium manganate in the application, the chemical reactions occurring in the synthesis process are as follows:

[0022] 3Mn 6+ +Fe+4OH - →3Mn 4+ +Fe 2+ +O2+2H2O

[0023] 4Fe 2+ +O2+2H2O→4Fe 3+ +4OH -

[0024] Mn 4+ +2Fe 3+ +10OH -→ Mn-2FeOOH + 4H2O

[0025] Another object of the present application is to provide an application of the iron negative electrode material with excellent performance in the preparation of aqueous alkaline batteries, which can have excellent electrochemical performance and stability.

[0026] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0027] The iron negative electrode material of the present application is obtained by using an iron substrate as an iron source and by simply immersing it in a mixed solution containing a high-valence manganese compound and a thiosulfate salt. The high-valence manganese compound reacts with the iron substrate, water and oxygen under alkaline conditions to oxidize the iron into FeOOH, and part of the manganese elements can also enter the crystal lattice of FeOOH during the reaction to form Mn-doped FeOOH. The thiosulfate salt is a sulfur source and also provides a weak alkaline environment for the reaction, thereby accelerating the reaction; part of the sulfur elements in the thiosulfate salt can be adsorbed on the surface of the FeOOH product or doped into the crystal lattice during the reaction. The high-valence manganese compound and the thiosulfate salt work together to ultimately form Mn and S co-doped FeOOH material.

[0028] The iron negative electrode material of the present application has a high specific surface area, excellent electrical conductivity, high capacity and good rate performance, and has better energy storage performance than most of the currently reported iron-based negative electrodes. The in-situ generated FeOOH material on the iron substrate does not require additional binders, conductive agents and metal current collectors. The synthesis method provided is not only simple to operate and easy to implement, but also has simple and readily available raw materials, low cost and almost no consumption, which can meet the requirements of large-area synthesis and be widely used in industrial production. The present application provides a high-performance negative electrode material for the development of aqueous alkaline batteries and has a broad application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 Fig. (a) is a high-rate scanning electron microscope (SEM) image of the iron negative electrode material of Example 1, and Figs. (b) and (c) are transmission electron microscope (TEM) images of the iron negative electrode material of Example 1.

[0030] Figure 2 Fig. is a high-resolution transmission electron microscope (HRTEM) image and the corresponding element distribution map of the iron negative electrode material of Example 1.

[0031] Figure 3 Fig. is a cyclic voltammetry curve (CV) of the iron negative electrode material of Example 1 in a 6M KOH solution at 10mV s -2

[0032] Figure 4 Fig. is a charge-discharge curve of the iron negative electrode material of Example 1 at different current densities.

[0033] ​Figure 5 Cycle life curve of the iron anode material of Example 1. DETAILED DESCRIPTION

[0034] The present application will be further described in conjunction with specific examples and drawings, but the examples do not limit the present application in any form. Unless otherwise specified, the reagents, methods and equipment used in the present application are conventional reagents, methods and equipment in the technical field.

[0035] Unless otherwise specified, the reagents and materials used in the present application are commercially available.

[0036] The iron anode material of the present application is prepared by an ultrafast low-temperature self-corrosion method, and the steps of the synthesis method are as follows:

[0037] S1. Iron substrate cleaning: foam iron (2 cm x 3 cm) is sequentially cleaned with 1 mol / L hydrochloric acid, acetone, deionized water, and ethanol for 10 min to remove surface impurities and oxide layers, and clean foam iron is obtained;

[0038] S2. Low-temperature synthesis of iron anode material: the clean foam iron obtained in S1 is immersed in a solution containing a high-valence manganese compound and a thiosulfate salt for a certain time to obtain an iron anode material, and the iron anode material is taken out and sequentially cleaned with deionized water and ethanol solution and dried at 60°C.

[0039] The reaction conditions of each embodiment and comparative example of the present application, and the performance test results are shown in the following table. Among them, the reaction solution of Comparative Example 5 is an aqueous solution, the reaction solution of Comparative Example 6 is a sodium thiosulfate solution, and the reaction solution of Comparative Example 7 is a potassium permanganate solution.

[0040]

[0041]

[0042] The iron anode material prepared in Example 1 was subjected to detailed performance testing, and the test results are shown in Figures 1 to 5 From Figure 1 (a), it can be seen that uniform nanoclusters are grown in situ on the surface of the foam iron substrate; from (b) and (c), it can be seen that the nanoclusters are composed of irregular ultrathin nanosheets less than 100 nm. From the HRTEM image of Figure 2 , it can be seen that polycrystalline FeOOH (JCPDS: 76-2301) is generated on the surface of the foam iron substrate, and the lattice fringes of 2.11 nm and 2.66 nm correspond to the (011) and (111) crystal planes of FeOOH, respectively; the element distribution map clearly shows that elements Fe, Mn, O, and S are uniformly distributed on the surface of the foam iron substrate, indicating that the Mn and S co-doped FeOOH product is synthesized. Figure 3The CV curve of the iron negative electrode material indicates that the highly reversible redox reaction of the iron negative electrode material in the aqueous KOH solution can be used as a high-performance water-based battery negative electrode material. Figure 4 It can be seen that the area capacity of the iron negative electrode material can reach 2.13mAh cm -2 at the current density of 10mA cm -2 ; in addition, with the increase of the current density, the area capacity has little increase, and when the current density increases to 60mA cm -2 , the area capacity can still reach 0.7mAh cm -2 , indicating that the iron negative electrode material has high area capacity and good rate performance, and excellent energy storage performance. Figure 5 The iron negative electrode material has good stability, and can be stably cycled for more than 8000 cycles at the current density of 30mA cm -2 , and the coulombic efficiency almost has no attenuation.

[0043] Obviously, the above embodiments of the present application are only examples for clearly illustrating the present application, and are not intended to limit the implementation modes of the present application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, it is not necessary and impossible to enumerate all the implementation modes. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. An iron negative electrode material with excellent performance, comprising an iron base, characterized in that, The iron substrate is in-situ generated with manganese and sulfur co-doped iron oxyhydroxide material on its surface by solution immersion; the solution comprises water, high-valence manganese compound and thiosulfate; the molar ratio of high-valence manganese compound and thiosulfate in the solution is 5-10:1; the concentration of high-valence manganese compound and thiosulfate in the solution is 0.01-0.3 mol / L and 0.001-0.05 mol / L, respectively; the immersion time is 3-30 min, the solution immersion temperature is 25-40 ℃, and the pH value is 7.01-9; the iron oxyhydroxide is formed by nanosheets with a size of 10-100 nm, and the nanosheets form a nano-cluster structure.

2. The excellent-performance iron negative electrode material according to claim 1, characterized by The high-valence manganese compound is selected from one or both of potassium permanganate and potassium manganate.

3. The excellent-performance iron negative electrode material according to claim 1, characterized by The thiosulfate is selected from one or more of potassium thiosulfate, ammonium thiosulfate, sodium thiosulfate, lithium thiosulfate, and calcium thiosulfate.

4. The method of claim 1, wherein the performance excellent iron negative material is synthesized at a superfast low temperature. The method comprises the following steps: S1. Iron substrate cleaning: commercially available iron materials are sequentially cleaned with hydrochloric acid, acetone, deionized water, and ethanol to remove surface impurities and oxide layers, and obtain clean iron substrates; S2. Low-temperature synthesis of iron negative electrode material: the clean iron substrate obtained in S1 is immersed in a solution containing high-valence manganese compound and thiosulfate for a certain time to obtain an iron negative electrode material, and the iron negative electrode material is taken out and sequentially cleaned with deionized water and ethanol solution and dried; the high-valence manganese compound is selected from one or both of potassium permanganate and potassium manganate, and the concentration is 0.01-0.3 mol / L; the thiosulfate is selected from one or more of potassium thiosulfate, ammonium thiosulfate, sodium thiosulfate, lithium thiosulfate, and calcium thiosulfate, and the concentration is 0.001-0.05 mol / L; the molar ratio of high-valence manganese compound and thiosulfate is 5-10:

1.

5. The ultrafast low-temperature synthesis process of claim 4, wherein, The reaction time in S2 is 3-30 min, the reaction temperature is 25-40 ℃, the reaction pH value is 7.01-9, and the drying temperature is 60-70 ℃; the cleaning time of the iron substrate in different washing solutions in S1 is 5-30 min, and the concentration of hydrochloric acid is 0.5-3 mol / L.

6. The application of the iron negative electrode material with excellent performance according to any one of claims 1-3 in an alkaline water-based battery.

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