A method for improving the performance of iron tetroxide (Fe3O4) as the negative electrode material in lithium-ion batteries.

Abstract

This invention discloses a method for improving the performance of Fe3O4 (Fe3O4) anode material in lithium-ion batteries. The main steps include: immersing pure copper foil in a mixed solution containing a certain concentration of CTAB and 0.7M CuSO4 to obtain a CuBr / Cu composite current collector; then, using Fe3O4 as the active material, preparing it as an electrode according to conventional methods. Charge-discharge tests are then performed. Results show that at 200 mA g… ‑1 At current densities, the initial discharge specific capacity of the electrode using CuBr / Cu current collector is 1.5 to 2.0 times that of the conventional Fe3O4 electrode, at 1000 mA g. ‑1 After 50 cycles at a current density, the discharge specific capacity of the CuBr / Cu current collector electrode is 1.5 to 3.4 times that of the conventional Fe3O4 electrode. Experiments demonstrate that by using a CuBr / Cu composite current collector, the capacity and rate performance of the Fe3O4 anode material can be significantly improved. This invention offers a simple preparation method, low cost, and promising commercial application prospects.

Description

Technical Field

[0001] This invention relates to the field of energy materials technology, and to a method for improving the performance of iron tetroxide (Fe3O4) batteries, which are negative electrode materials for lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries possess advantages such as high energy density, low self-discharge rate, no memory effect, long cycle life, and environmental friendliness, and are widely used in electronic products such as mobile phones, laptops, and smart wearable devices. Simultaneously, lithium-ion batteries are also a major power source for new energy vehicles, contributing to climate change mitigation and alleviating energy pressure. The anode material is a crucial component of lithium-ion batteries, significantly impacting their performance. Graphite is the most common commercially available anode material for lithium-ion batteries; however, graphite has a low theoretical specific capacity, its safety needs improvement, and its high-temperature resistance is insufficient. Therefore, modifying or developing new anode materials is of significant practical importance. Research has found that transition metal oxides such as Co3O4, CeO2, NiO, Fe3O4, and MnO2 possess high theoretical specific capacities and are promising candidates for lithium-ion battery anode materials, attracting extensive research. Among them, iron(III) oxide (Fe3O4) boasts a theoretical specific capacity as high as 926 mAh g⁻¹. -1 Fe3O4 is abundant, inexpensive, low-cost, and environmentally friendly, making it a promising candidate for future applications. However, studies have revealed that Fe3O4 exhibits low electrical conductivity and significant, irreversible volume fluctuations during charge and discharge. These shortcomings result in poor cycle stability and rate performance, severely hindering its further commercial application.

[0003] Literature review shows that there are currently two main methods to improve the electrochemical performance of Fe3O4 anode materials: one is to prepare Fe3O4 with a special structure, and the other is to composite Fe3O4 with carbon materials to prepare carbon-based Fe3O4 materials. For example, CN110492079A proposes a method for preparing and applying a layered iron(III) oxide (Fe3O4) anode material. This patent utilizes the special morphology of Fe3O4 to improve its electrochemical performance to a certain extent. CN111129449A discloses a method for preparing and applying a graphene / carbon / Fe3O4 composite material. This patent significantly improves the conductivity of Fe3O4 through carbon doping, thereby optimizing its electrochemical performance. However, the above methods generally suffer from drawbacks such as complex preparation processes and high costs. Therefore, research on improving the electrochemical performance of Fe3O4 remains one of the hot topics in lithium-ion battery anode material research. Summary of the Invention

[0004] This experiment aims to provide a method for improving the performance of Fe3O4 batteries, which are negative electrode materials for lithium-ion batteries. This invention obtains CuBr-modified copper foil current collectors by controlling the amount of hexadecyltrimethylammonium bromide (CTAB), and uses these current collectors in Fe3O4 electrodes, resulting in significant improvements in the discharge specific capacity, rate performance, and cycle stability of Fe3O4.

[0005] The concept of this invention is as follows: A certain amount of hexadecyltrimethylammonium bromide (CTAB) is added to 100 ml of 0.7 M CuSO4 solution and mixed thoroughly to obtain a copper sulfate solution containing CTAB. Then, a dry, pure copper foil is placed in this solution and soaked for a certain period of time. After removing the copper foil, it is cleaned and dried at room temperature to obtain a CuBr-modified copper foil current collector (denoted as CuBr / Cu). Fe3O4 is then coated onto the current collector CuBr / Cu as the active material to complete the electrode preparation. This electrode is then assembled with a lithium element to form a half-cell, and its electrochemical performance is tested. The results show that this method can significantly improve the discharge specific capacity, rate performance, and cycle stability of Fe3O4. Literature review shows that research on improving the electrochemical performance of Fe3O4 by modifying current collectors has not been reported domestically or internationally.

[0006] The preparation method of the present invention includes the following specific steps:

[0007] (1) Preparation of materials

[0008] Iron(III) oxide (Fe3O4) powder, hexadecyltrimethylammonium bromide (CTAB), CuSO4 solution, commercial copper foil, double-distilled water, acetylene black, polyvinylidene fluoride (PVDF), N-methylpyrrolidone (NMP), organic electrolyte, and diaphragm (Celgard 2400 microporous polypropylene membrane).

[0009] (2) Preparation of current collector and Fe3O4 electrode

[0010] (2-1) Preparation of copper foil current collector and Fe3O4 electrode

[0011] The copper foil was wiped clean with ethanol solution and dried at room temperature to obtain a clean copper foil current collector, denoted as current collector o. Using Fe3O4 as the active material, Fe3O4 powder, acetylene black, and PVDF were mixed in a mass ratio of 8:1:1. The mixture was thoroughly ground in a mortar for 20 minutes. Then, 15-25 drops of N-methylpyrrolidone (NMP) were added to the ground mixture while stirring to obtain a paste. The paste was then evenly spread onto the prepared clean copper foil current collector using a smearer and vacuum dried at 100-120℃ for 5-8 hours. This completed the preparation of the Fe3O4 electrode, denoted as electrode o.

[0012] (2-2) Preparation of CuBr / Cu current collector and modified Fe3O4 electrode

[0013] First, prepare 100 ml of 0.7 M CuSO4 solution, then add a certain amount of CTAB to this solution, mix thoroughly, and sonicate for 8-12 min to form 100 ml of a mixed solution containing 2-12 mM CTAB and 0.7 M CuSO4. Place a clean copper foil into this mixed solution, immerse it at room temperature for 8-15 min, then remove it, rinse with distilled water, and dry at room temperature to obtain a CuBr / Cu composite current collector, denoted as current collector a. Next, prepare an electrode following the same process as the Fe3O4 electrode, except that a composite current collector is used this time, resulting in a modified Fe3O4 electrode, denoted as electrode a. Finally, assemble electrodes a and a with elemental lithium sheets to form batteries, and test the electrochemical performance of the batteries.

[0014] (3) Determination of battery electrochemical performance

[0015] The prepared electrodes and other materials were placed in a glove box, which was then filled with high-purity nitrogen gas before assembling the half-cell. The separator used for assembling the half-cell was a Celgard 2400 microporous polypropylene membrane, and the organic electrolyte solution was LiPF6 dissolved in an organic solvent. Constant current charge-discharge tests were conducted on a charge-discharge instrument (CT-3008W-5V20mA-S4) from Shenzhen Xinwei Electronics Co., Ltd.

[0016] The results showed that at 200 mA g -1 At current density, the initial discharge specific capacity of the modified electrode a is 1100~1500 mAh g. -1 It is 1.5 to 2.0 times that of traditional Fe3O4 electrodes. At 1000 mA g -1 After 50 cycles at a current density, the discharge specific capacity of electrode a is 1.5 to 3.4 times that of electrode o. Experiments demonstrate that by using a CuBr / Cu composite current collector, the capacity and rate performance of the Fe3O4 anode material can be significantly improved.

[0017] As a preferred condition, a 100 ml mixed solution containing 2-12 mM CTAB and 0.7 M CuSO4 is formed, with the most favorable condition being a mixed solution containing 6 mM CTAB.

[0018] The copper foil immersion time is 8-15 minutes, with the optimal immersion time being 10 minutes.

[0019] The Fe3O4 powder used was of analytical grade.

[0020] The organic electrolyte is a 1 mol / L LiPF6 organic electrolyte.

[0021] Commercial copper foil was selected.

[0022] The beneficial effects of this invention are as follows: using a CuBr / Cu composite current collector can significantly improve the capacity and rate performance of the Fe3O4 electrode. Remarkably, at 1000 mA g... -1 After 50 cycles at the current density, the discharge specific capacity of the Fe3O4 electrode prepared using the composite current collector is 1.5 to 3.4 times that of the conventional Fe3O4 electrode, exhibiting excellent cycle stability. This invention is simple to operate; a CuBr-coated current collector can be obtained through a simple room-temperature impregnation process, and this current collector can significantly improve the electrochemical performance of the Fe3O4 anode material. This invention has advantages such as simple preparation method, clean and pollution-free preparation process with no energy consumption, and low cost, making it of great potential commercial value. Attached Figure Description

[0023] Figure 1 These are the standard XRD patterns of the surface material of current collector a and CuBr and Cu; line a corresponds to the XRD pattern of the sample scraped from the surface of the CuBr / Cu current collector.

[0024] Figure 2 A half-cell assembled with electrodes a and o was tested at 200 mA g. -1 The first charge-discharge curves at current density; line a corresponds to the Fe3O4 electrode using a composite current collector (CuBr / Cu), while line o corresponds to the conventional Fe3O4 electrode using the original copper foil.

[0025] Figure 3 The magnification diagrams are for electrodes a and o; line a corresponds to the Fe3O4 electrode using a composite current collector (CuBr / Cu), while line o corresponds to the conventional Fe3O4 electrode using the original copper foil.

[0026] Figure 4 A half-cell assembled with electrodes a and o at 1000 mA g -1 50-cycle long-cycle diagram at current density; where line a corresponds to the Fe3O4 electrode using a composite current collector (CuBr / Cu), while line o corresponds to the conventional Fe3O4 electrode using the original copper foil. Detailed Implementation

[0027] The following examples are used to illustrate the present invention.

[0028] Example 1

[0029] Commercial copper foil was wiped clean with double-distilled water and ethanol solution, and dried at room temperature to obtain a clean copper foil current collector, denoted as current collector o. Using Fe3O4 as the active material, Fe3O4 powder, acetylene black, and PVDF were mixed in a mass ratio of 8:1:1. The mixture was then thoroughly ground in a mortar for 20 min. Next, 20 drops of N-methylpyrrolidone (NMP) were added to the ground mixture while stirring to obtain a paste. The paste was then evenly spread onto the clean copper foil current collector using a smearer, and vacuum dried at 120°C for 6 hours. This completed the preparation of the Fe3O4 electrode using the original copper foil as the current collector, denoted as electrode o.

[0030] Prepare 100 ml of 0.7 M CuSO4 solution, then add a certain amount of CTAB to the solution, sonicate for 10 min to mix thoroughly, forming 100 ml of a mixed solution containing 6 mM CTAB + 0.7 M CuSO4. Next, immerse a clean copper foil in this mixed solution at room temperature for 10 min, then remove it, rinse with distilled water, and dry at room temperature to obtain a CuBr / Cu composite current collector, denoted as current collector a. Then, prepare an electrode following the same process as the Fe3O4 electrode, the only difference being that the prepared composite current collector is used, resulting in an Fe3O4 electrode using the CuBr / Cu composite current collector, denoted as electrode a. Finally, assemble electrodes a and a with elemental lithium sheets to form half-cells, and test the electrochemical performance of the cells.

[0031] The assembly of the half-cell was carried out in a glove box filled with high-purity nitrogen. The separator used in the battery assembly was a Celgard 2400 microporous polypropylene membrane, and the organic electrolyte solution was LiPF6 dissolved in an organic solvent. Constant current charge-discharge tests were performed on a charge-discharge instrument (CT-3008W-5V20mA-S4) from Shenzhen Xinwei Electronics Co., Ltd. The results showed that at 200mA g… -1 At current density, the initial discharge specific capacity of electrode a is 1100~1500 mAh g. -1 It is 1.5 to 2.0 times that of traditional Fe3O4 electrodes. At 1000 mA g -1 After 50 cycles at a current density, the discharge specific capacity of electrode a is 1.5 to 3.4 times that of electrode o. Experiments demonstrate that using CuBr-modified copper foil current collectors can significantly improve the capacity and rate performance of Fe3O4 anode materials. Literature review shows that this work has not yet been reported domestically or internationally.

[0032] Attached Figure Description Figure 1The XRD pattern of the sample scraped from the surface of current collector a, and the standard cards for CuBr and Cu are shown. It can be seen that the sample corresponds to the Cu standard card (JCPDS, No: 01-1241), which is because a small amount of elemental Cu on the copper foil was also scraped off during the sample scraping process. The sample also corresponds to the CuBr standard card (JCPDS, No: 73-1497), indicating that the product on the surface of the copper foil after immersion in a mixed solution of 6 mM CTAB + 0.7 M CuSO4 is CuBr.

[0033] Figure 2 Electrode o and electrode a at 200 mA g -1 The initial charge-discharge curves at the current density are shown. It can be seen that the discharge specific capacity of the Fe3O4 electrode using the original copper foil is 744 mAh g⁻¹. −1 The discharge specific capacity of the Fe3O4 electrode using CuBr / Cu current collector is 1475 mAh g. −1 Its discharge specific capacity is 2.0 times that of the traditional Fe3O4 electrode. This indicates that the use of CuBr / Cu composite current collector significantly improves the discharge specific capacity of the Fe3O4 anode material.

[0034] Figure 3 Electrode o and electrode a are respectively at 200 mA g -1 500 mA g -1 1000 mA g -1 200 mA g -1 The graph shows the relationship between the discharge specific capacity and the number of cycles after 10 cycles at a given rate. Line o corresponds to the Fe3O4 electrode using the original copper foil current collector, and line a corresponds to the Fe3O4 electrode using the CuBr / Cu composite current collector. It can be seen that at every current density, the discharge specific capacity of electrode a is higher than that of electrode o, indicating that the CuBr / Cu composite current collector has superior electrochemical performance, and the Fe3O4 electrode using the composite current collector has better rate performance.

[0035] Figure 4 For electrodes o and a at 1000mA g -1 The graph shows the relationship between discharge specific capacity and cycle number after 50 cycles at a given current density. Line o corresponds to the Fe3O4 electrode using the original copper foil current collector, and line a corresponds to the Fe3O4 electrode using the CuBr / Cu composite current collector. It can be seen that the discharge specific capacity of electrode a is always higher than that of electrode o, and after 50 cycles, the discharge specific capacity of electrode a is 316 mAh g⁻¹. −1 The discharge specific capacity of electrode o is 97 mAh g. -1The discharge specific capacity of the Fe3O4 electrode using the CuBr / Cu composite current collector is 3.3 times that of the Fe3O4 electrode using the original copper foil current collector. This indicates that the Fe3O4 electrode assembled with the CuBr / Cu composite current collector has a higher discharge specific capacity.

[0036] Example 2

[0037] An Fe3O4 electrode using raw copper foil as the current collector was prepared according to Example 1 and named electrode o. A mixed solution containing 4 mM CTAB + 0.7 M CuSO4 was prepared in 100 ml. A clean copper foil was immersed in this mixed solution for 8 min at room temperature. Subsequent operations were performed as in Example 1 to obtain a CuBr / Cu composite current collector and an Fe3O4 electrode assembled using the composite current collector, named electrode a. Electrodes o and a were assembled with elemental lithium sheets to form half-cells, and battery performance was tested.

[0038] The results showed that at 200 mA g -1 At the current density, the initial discharge specific capacity of electrode a is 1190 mAh g. -1 It is 1.6 times that of electrode o. At 1000 mA g -1 After 50 cycles at the current density, the discharge specific capacity of electrode a is 1.8 times that of electrode o.

[0039] Example 3

[0040] An Fe3O4 electrode using raw copper foil as the current collector was prepared according to Example 1 and named electrode o. A mixed solution containing 5 mM CTAB + 0.7 M CuSO4 was prepared in 100 ml. A clean copper foil was immersed in this mixed solution for 9 min at room temperature. Subsequent operations were performed as in Example 1 to obtain a CuBr / Cu composite current collector and an Fe3O4 electrode assembled using the composite current collector, named electrode a. Electrodes o and a were assembled with elemental lithium sheets to form half-cells, and battery performance was tested.

[0041] The results showed that at 200 mA g -1 At the current density, the initial discharge specific capacity of electrode a is 1300 mAh g. -1 It is 1.7 times that of electrode o. At 1000 mA g -1 After 50 cycles at the current density, the discharge specific capacity of electrode a is 2.7 times that of electrode o.

[0042] Example 4

[0043] An Fe3O4 electrode using raw copper foil as the current collector was prepared according to Example 1 and named electrode o. A mixed solution containing 8 mM CTAB + 0.7 M CuSO4 was prepared in 100 ml. A clean copper foil was immersed in this mixed solution for 10 min at room temperature. Subsequent operations were performed as in Example 1 to obtain a CuBr / Cu composite current collector and an Fe3O4 electrode assembled using the composite current collector, named electrode a. Electrodes o and a were assembled with elemental lithium sheets to form half-cells, and battery performance was tested.

[0044] The results showed that at 200 mA g -1 At the current density, the initial discharge specific capacity of electrode a is 1120 mAh g. -1 It is 1.5 times that of electrode o. At 1000 mA g -1 After 50 cycles at the current density, the discharge specific capacity of electrode a is 1.5 times that of electrode o.

[0045] Example 5

[0046] An Fe3O4 electrode using pristine copper foil as the current collector was prepared according to Example 1 and named electrode o. A mixed solution containing 7 mM CTAB + 0.7 M CuSO4 was prepared in 100 ml. A clean copper foil was immersed in this mixed solution for 11 min at room temperature. Subsequent operations were performed as in Example 1 to obtain a CuBr / Cu composite current collector and an Fe3O4 electrode assembled using the composite current collector, named electrode a. Electrodes o and a were assembled with elemental lithium sheets to form half-cells, and battery performance was tested.

[0047] The results showed that at 200 mA g -1 At the current density, the initial discharge specific capacity of electrode a is 1320 mAh g. -1 It is 1.8 times that of electrode o. At 1000 mA g -1 After 50 cycles at the current density, the discharge specific capacity of electrode a is 2.5 times that of electrode o.

[0048] Example 6

[0049] An Fe3O4 electrode using raw copper foil as the current collector was prepared according to Example 1 and named electrode o. A mixed solution containing 6 mM CTAB + 0.7 M CuSO4 was prepared in 100 ml. A clean copper foil was immersed in this mixed solution for 12 min at room temperature. Subsequent operations were performed as in Example 1 to obtain a CuBr / Cu composite current collector and an Fe3O4 electrode assembled using the composite current collector, named electrode a. Electrodes o and a were assembled with elemental lithium sheets to form half-cells, and battery performance was tested.

[0050] The results showed that at 200 mA g-1 At the current density, the initial discharge specific capacity of electrode a is 1400 mAh g. -1 It is 1.9 times that of electrode o. At 1000 mA g -1 After 50 cycles at the current density, the discharge specific capacity of electrode a is 3.1 times that of electrode o.

Claims

1. A method for improving the performance of iron oxide (Fe3O4) as the negative electrode material in lithium-ion batteries, characterized in that, Includes the following steps: (1) Material preparation Fe3O4 powder, CTAB, CuSO4 solution, copper foil, double-distilled water, acetylene black, PVDF, N-methylpyrrolidone, organic electrolyte, diaphragm; (2) Preparation of current collector and Fe3O4 electrode (2-1) Preparation of copper foil current collector and Fe3O4 electrode The copper foil was wiped clean with ethanol solution and dried at room temperature to obtain a clean copper foil current collector, denoted as current collector o. Using Fe3O4 as the active material, Fe3O4 powder, acetylene black, and PVDF were mixed in a mass ratio of 8:1:

1. The resulting mixture was thoroughly ground in a mortar. Then, 15-25 drops of N-methylpyrrolidone were added to the ground mixture while stirring to obtain a paste. The paste was then evenly spread on current collector o using a smearer and vacuum dried at 100-120°C for 5-8 hours to complete the preparation of the Fe3O4 electrode, denoted as electrode o. (2-2) Preparation of CuBr / Cu current collector and modified Fe3O4 electrode First, prepare a 0.7M CuSO4 solution, then add a certain amount of CTAB to the solution, mix thoroughly, and sonicate for 8-12 minutes to form a mixed solution containing 2-12mM CTAB and 0.7M CuSO4; immerse the copper foil in the mixed solution, remove it at room temperature for 8-15 minutes, rinse it with double-distilled water and dry it at room temperature to obtain the CuBr / Cu composite current collector, denoted as current collector a; The paste was then evenly spread onto current collector a using a smearer to obtain a modified Fe3O4 electrode, which was designated as electrode a. Finally, electrode o and electrode a were assembled with elemental lithium sheets to form a battery, and the electrochemical performance of the battery was tested.

2. The method for improving the performance of iron tetroxide (Fe3O4) as the negative electrode material of lithium-ion batteries according to claim 1, characterized in that, Prepare a 100ml mixed solution containing 2-12mM CTAB and 0.7M CuSO4.

3. The method for improving the performance of iron tetroxide (Fe3O4) as the negative electrode material of lithium-ion batteries according to claim 2, characterized in that, The mixed solution contains 6 mM CTAB and 0.7 M CuSO4.

4. The method for improving the performance of iron tetroxide (Fe3O4) battery anode material according to claim 1, characterized in that, Copper foil is used as the negative electrode current collector in commercial lithium batteries.

5. A method for improving the performance of iron tetroxide (Fe3O4) as the negative electrode material of a lithium-ion battery according to claim 1, characterized in that, The copper foil was placed in the mixed solution and immersed at room temperature for 10 minutes before being removed.

6. The method for improving the performance of iron tetroxide (Fe3O4) as the negative electrode material of lithium-ion batteries according to claim 1, characterized in that, The Fe3O4 powder was of analytical grade.

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