A nano-Fe9S 10 @C Preparation method of lithium ion battery negative electrode composite material

Abstract

The present invention relates to a nano Fe9S 10 @C A method for preparing a negative electrode composite material for a lithium-ion battery comprises the following steps: adding gelatin to deionized water, heating the mixture in a water bath while stirring, and turning the solution into a light yellow transparent gel solution; then adding FeSO4·7H2O, stirring the mixture at 60‑80°C for 8‑12 minutes, cooling the mixture naturally, forming a solid colloidal substance, and drying the mixture; heating the mixture in a tubular furnace and maintaining a constant temperature, and then cooling the mixture naturally to obtain the finished product. The advantages are: using a one-step method, the active material is uniformly coated during the high-temperature carbonization process to form a carbon-coated nanocomposite material. This method uses inexpensive and readily available gelatin as the base carbon, and FeSO4·7H2O as both the iron source and the sulfur source, which are dissolved in the gelatin gel solution, cooled, and further carbonized to form Fe9S with good conductivity. 10 @C nanocomposite materials.

Description

Technical Field

[0001] The present invention belongs to the field of lithium ion battery negative electrode materials, and in particular relates to a nano Fe9S 10 @C Preparation method of lithium-ion battery negative electrode composite material. Background Art

[0002] With the growing demand for energy storage in portable electronic devices, hybrid vehicles, and large-scale power grids, the development of high-energy-density and high-power-density energy storage devices is urgent. Lithium-ion batteries (LIBs) theoretically offer a high energy density of 150 Wh / kg, but their inherently slow solid-state diffusion and volumetric strain result in low power density. Therefore, the preparation of high-performance anode materials is crucial.

[0003] Research on high-performance lithium-ion anode materials primarily includes materials based on intercalation reactions (such as TiO2), materials based on conversion reactions (such as Fe2O3, Fe2O3, FeS, etc.), and alloy materials (such as SnO2, SnS2, etc.). Iron sulfides have attracted widespread attention due to their high lithium storage capacity and high natural abundance. However, as lithium-ion anode materials, iron sulfides often suffer from poor electrical conductivity and a prohibitive large volume expansion during lithium storage and de-lithiation. To obtain anode materials with superior lithium storage performance, significant electrical conductivity and a more stable structure are required. This is because only fast electron transport and a stable structure can lead to rapid and complete electrochemical reactions, allowing the active material to fully realize its desired lithium storage capacity.

[0004] So far, the most effective method is to combine high theoretical capacity iron sulfide negative electrode materials with cheap and readily available conductive base carbon materials. However, for traditional composite methods, such as coating and mechanical mixing, the interfacial contact resistance is often unfavorable for the storage of lithium in active materials. The main reason is that the conductive network is composed of physical interconnections rather than chemical bonds, and the transmission of electrons needs to overcome a large resistance, resulting in unsatisfactory electrochemical performance. In addition, the microscopic size of iron sulfide is also a key factor affecting its electrochemical performance. Nanosized iron sulfide is also favored by researchers because its lattice structure is not easily destroyed during lithium storage. However, traditional methods for preparing nanomaterials often require a high temperature and high pressure environment, and the prospects for industrial production are not clear. Therefore, how to construct a highly conductive carbon network to prepare iron sulfide nanocomposite electrodes with large capacity, good rate performance and long cycle stability is imminent. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a nano-Fe9S 10 Preparation method of lithium-ion battery negative electrode composite material, using gelatin-based carbon coated Fe9S 10Preparation of negative electrode materials for lithium-ion batteries, enhanced Fe9S 10 Lithium storage properties of materials.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A nano-Fe9S 10 A method for preparing a lithium-ion battery negative electrode composite material comprises the following steps:

[0008] 1) Add gelatin to deionized water and heat in a water bath while stirring. Heat to 60-80°C and hold the temperature constant for 3-6 minutes until the solution becomes a slightly yellow, transparent gel solution.

[0009] 2) adding FeSO4·7H2O to the yellowish transparent gel solution of step 1), stirring at 60-80°C for 8-12 minutes, cooling naturally to form a solid colloidal substance, and then drying in a drying oven at 70-90°C for 10-14 hours;

[0010] 3) The dried material was placed in a corundum boat and heated in a tube furnace for 1.5-2.5 hours to 450-550°C, and kept at a constant temperature for 0.5-1.5 hours under a nitrogen atmosphere, and then cooled naturally to obtain Fe9S 10 @C composite materials.

[0011] The amount of gelatin in step 1) is 1-6 g, and the amount of deionized water is 40-60 ml; the amount of FeSO4·7H2O in step 2) is 1.3-7 g.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] The preparation method of the present invention replaces the more expensive carbon source and high-temperature and high-pressure methods required to prepare nanocomposites. Because gelatin forms a colloid when heated with water and has numerous cation attachment points within it, it facilitates uniform dispersion of cations. A one-step process is employed to uniformly coat the active material during high-temperature carbonization to form a carbon-coated nanocomposite. The present invention utilizes inexpensive and readily available gelatin as the carbon base and FeSO4·7H2O as both the iron and sulfur sources. These are dissolved in a gelatin solution, cooled, and further carbonized to form Fe9S2O, a highly conductive nanocomposite. 10 @C nanocomposite material. Fe9S 10 @C composite material is used as the negative electrode material of lithium-ion half-cells, and when the carbon content is 42%, the electrochemical performance of the composite material is the best, with a discharge capacity of 712.2 mAh / g after 100 cycles at 0.1 A / g, and a reversible capacity of 298.5 mAh / g after 200 cycles at a current density of 1 A / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is Fe9S 10 @XRD pattern of C composite material.

[0015] Figure 2 It is Fe9S 10 @CTEM image of the composite material.

[0016] Figure 2 (a) is the TEM image of FS@C-1.39 composite material; (b) is the TEM image of FS@C-2.78 composite material; (c) is the TEM image of FS@C-4.17 composite material; (d) is the TEM image of FS@C-6.95 composite material.

[0017] Figure 3 It is Fe9S 10 @CThermogravimetric curve of composite material.

[0018] Figure 4 This is the XPS graph of FS@C-4.17 composite material.

[0019] Figure 5 (a) is Fe9S 10 @C composite material cycle performance diagram; (b) is Fe9S 10 @C composite material rate performance diagram; (c) is Fe9S 10 @CComposite material long cycle performance diagram. DETAILED DESCRIPTION

[0020] The present invention will be described in detail below with reference to the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0021] A nano-Fe9S 10 A method for preparing a lithium-ion battery negative electrode composite material comprises the following steps:

[0022] 1) Add 1-6g of gelatin to deionized water and heat in a water bath while stirring. Heat to 60-80°C and keep the temperature constant for 3-6 minutes until the solution becomes a slightly yellowish transparent gel solution.

[0023] 2) adding 1.3-7 g of FeSO4·7H2O to the slightly yellow transparent gel solution of step 1), stirring at 60-80°C for 8-12 minutes, cooling naturally to form a solid gel-like substance, and then drying in a drying oven at 70-90°C for 10-14 hours;

[0024] 3) The dried material was placed in a corundum boat and heated in a tube furnace for 1.5-2.5 hours to 450-550°C, and kept at a constant temperature for 0.5-1.5 hours under a nitrogen atmosphere, and then cooled naturally to obtain Fe9S 10 @C composite materials.

[0025] Example 1

[0026] Nano-Fe9S 10 A method for preparing a lithium-ion battery negative electrode composite material comprises the following steps:

[0027] (1) Weigh four portions of gelatin (5 g each) and add them to a beaker containing 50 ml of deionized water. Heat in a water bath while stirring. Heat to 70°C and keep the temperature constant for 5 minutes until the solution becomes a slightly yellowish transparent gel solution.

[0028] (2) 1.39 g, 2.78 g, 4.17 g, and 6.95 g of FeSO4·7H2O were added directly to the above four solutions, respectively, and stirred at 70°C for 10 min. The four solutions were then cooled naturally to transform into solid colloids, and then dried in a drying oven at 80°C for 12 h.

[0029] (3) The dried sample was placed in a corundum boat, heated to 450-550°C in a tube furnace for 2 hours, and kept at this temperature for 1 hour (under nitrogen atmosphere), and then cooled naturally to obtain Fe9S 10 @C composite materials.

[0030] According to the different amounts of FeSO4·7H2O added, the composite materials were named FS@C-1.39, FS@C-2.78, FS@C-4.17, and FS@C-6.95 (the numbers represent the amount of FeSO4·7H2O added, unit: g).

[0031] See Figure 1 The composite material Fe9S was successfully prepared by adding FeSO4·7H2O into the gelatin gel solution in one step and then further treating it at high temperature. 10 @C, from Figure 1 It can be seen that there is Fe9S in the composite material 10 phase, and the corresponding peak position corresponds to the standard card JCPDS Card No.34-1470, indicating that Fe9S 10 @C composite materials.

[0032] See Figure 2 (a), (b), (c), (d), Fe9S 10 In the composite material, they are all nanomaterials, but as Fe9S 10 The amount of Fe9S10 The Fe9S in the composite material is increasingly aggregated and presents a nanocluster structure. Secondly, when the amount of FeSO4·7H2O added is 4.17g, the Fe9S in the material 10 The distribution is relatively even.

[0033] The assembly process of lithium-ion batteries, including the preparation of electrode sheets and the process of assembling lithium-ion batteries, is as follows:

[0034] According to the mass ratio of 8:1:1, nano-Fe9S 10 The composite material, conductive agent (Super-P), and binder (PVDF) are ground and mixed evenly, and N-methylpyrrolidone (NMP) is added to form a viscous slurry, which is then evenly coated on the surface of the current collector (copper foil) using a coater.

[0035] The slurry-coated copper foil was placed in a vacuum oven at 120°C for 12 hours to remove the NMP solvent. Finally, the copper foil was cut into circular electrode sheets with a diameter of 11 mm for later use. CR2032 button cells were then assembled in an argon-filled glove box, where the lithium sheet served as both the counter electrode and the reference electrode. The entire process of encapsulating the lithium-ion battery was performed in an argon-filled glove box (water and oxygen contents were both less than 0.1 ppm).

[0036] See Figure 3 Thermogravimetric testing was performed at a heating rate of 10°C / min, a temperature range of 30-800°C, and an air atmosphere. Figure 3 As shown in the figure, the decrease in mass at temperatures of 30-107°C is mainly due to the loss of water in the material; the slight increase in mass in the temperature range of 107-310°C may be due to the 10 Oxidation is caused by FeSO4; when the temperature rises to 453℃, the huge mass loss is attributed to the combustion of carbon materials and Fe9S 10 Oxidized to Fe2O3; when the temperature continues to rise to 615℃, the mass loss is caused by the high-temperature decomposition of FeSO4 into Fe2O3, SO2, and O2. According to the final amount of Fe2O3, the carbon content in the composite material is calculated to be 77%, 65%, 58%, and 35% respectively (the corresponding Fe9S 10 The contents of PEG-1 were 23%, 35%, 42% and 65% respectively).

[0037] In the C1s spectrum (such as Figure 4 (a) shows that the peaks at binding energies of 284.3 eV, 285.5 eV, and 288.1 eV correspond to CC, CO, and C=O functional groups, respectively. A small amount of CO and C=O functional groups is beneficial for the fixation of Fe9S 10active sites, connecting the carbon material and the active substance through chemical bonds. Figure 4 (b) is the O1s XPS spectrum of the FS@C-4.17 composite material. The peaks at 529.4, 531.0, and 532.9 eV correspond to Fe-O, CO, and O–C=O functional groups, respectively. The presence of Fe-O proves that Fe9S 10 There is an interaction between the active material and the carbon shell, indicating that there is a chemical bond between the active material and the carbon in the prepared composite material. This chemical bond can be Fe9S 10 Provides excellent conductive network during lithium storage and lithium insertion to play the role of Fe9S 10 The maximum lithium storage capacity. In the S 2p spectrum ( Figure 4 In (c), the peak at 160.9 eV is the S 2- The corresponding characteristic peak at 163.3 eV is S in the oxidized state. n 2- The characteristic peak of 167.9eV is the peak of S 2p 1 / 2 spin orbit. Figure 4 (d) is the Fe 2p XPS spectrum of the FS@C-4.17 composite material. The peaks at binding energies of 712.6.7 eV and 724.1 eV are Fe 2+ The peak at the binding energy of 710.1 eV can be attributed to Fe 3+ state, indicating that there are two valence states of Fe in the material, and further confirming that Fe9S 10 The existence of phase.

[0038] from Figure 5 (a) It can be seen that compared with pure carbon, FS@C-1.39, and FS@C-6.95, the FS@C-2.78 and FS@C-4.17 composites have the best cycling performance. At a current density of 0.1 A / g, the reversible discharge specific capacities of the FS@C-2.78 and FS@C-4.17 composites after 100 cycles are 690.2 mAh / g and 640.5 mAh / g, respectively. The reversible discharge specific capacities of the pure carbon, FS@C-1.39, and FS@C-6.95 composites after 100 cycles are 156.1 mAh / g, 313.8 mAh / g, and 303.8 mAh / g, respectively.

[0039] like Figure 5 As shown in (b), the discharge specific capacities of FS@C-4.17 at current densities of 0.1 A / g, 0.2 A / g, 0.5 A / g, and 1 A / g are 712.2 mAh / g, 505.7 mAh / g, 397.5 mAh / g, and 282.2 mAh / g, respectively, which are all higher than the rate performance of other composite materials. When the current is restored to 0.1 A / g, it still has a reversible specific capacity of 742.5 mAh / g.

[0040] At the same time, if Figure 5 As shown in (c), the reversible capacity of FS@C-4.17 is 298.5 mAh / g after 200 cycles at a current density of 1 A / g, indicating that the structure of the FS@C-4.17 composite material is relatively stable.

[0041] The above electrochemical experimental results show that the present invention can prepare Fe9S with a large amount of conductive network through a simple preparation process. 10 @C nanocomposite material effectively improves the Fe9S 10 The electrochemical properties of nano-Fe9S 10 @C Gelatin-based composite materials show strong applicability in the preparation of carbon negative electrodes and also provide a reliable experimental basis for the preparation of other nanocomposites.

Claims

1. A nano-Fe9S 10 @C A method for preparing a negative electrode composite material for a lithium ion battery, characterized in that: The following steps are involved: 1) Add gelatin to deionized water and heat in a water bath while stirring. Heat to 60-80°C and maintain the temperature for 3-6 minutes until the solution becomes a slightly yellowish transparent gel solution. The amount of gelatin is 1-6g and the amount of deionized water is 40-60ml. 2) Add the yellowish transparent gel solution from step 1) , stirring at 60-80°C for 8-12 minutes, cooling naturally to form a solid colloidal substance, and then drying in a drying oven at 70-90°C for 10-14 hours; 1.3-7g; 3) Place the dried material into a corundum boat and heat it in a tube furnace for 1.5-2.5 hours to 450-550°C, and maintain the temperature for 0.5-1.5 hours under a nitrogen atmosphere, and then cool it naturally to obtain Fe9S 10 @C composite materials.

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