Preparation method of sphere-like iron chlorosulfide lithium ion battery negative electrode material

Abstract

The invention belongs to the technical field of lithium ion batteries, and discloses a preparation method of a spheroidal iron chlorosulfide lithium ion battery negative electrode material. According to the method, ferric chloride and sodium sulfide or thioacetamide are mixed in water according to a certain proportion, then a certain amount of surfactant is added, the mixture is transferred into a high-pressure kettle after being uniformly mixed, the mixture is heated and subjected to heat preservation for a period of time, a product is filtered, washed, dried and the like, and the spheroidal iron chlorosulfide lithium ion battery negative electrode material is obtained. The spheroidal iron chlorosulfide lithium ion battery negative electrode material prepared by the method disclosed by the invention is spheroidal, the first efficiency is up to 77% under the current density of 0.2 A / g, and the first circle discharge specific capacity reaches 1554mAh / g. The preparation method is simple, good in repeatability and low in cost. The obtained spherical-like iron chlorosulfide lithium ion battery negative electrode material solves the problems of small storage amount, high price, low theoretical specific capacity, high toxicity and the like of the traditional alloy lithium ion battery negative electrode material.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ion batteries, and specifically provides a method for preparing a quasi-spherical iron chlorosulfide lithium ion battery negative electrode material. Background Art

[0002] The rapid development of portable electronic devices and electric vehicles has prompted people to put forward higher requirements for the energy density of lithium-ion batteries. The development of high-capacity, large resource reserves, and non-toxic negative electrode materials is not only the key to improving the energy density of lithium-ion batteries, but also meets the needs of the "dual carbon" strategy. In traditional LIBS, the negative electrode is based on graphite. However, the theoretical capacity of graphite is very low (the theoretical capacity of LiC6 is 372mAh / g). Recently, alloy materials have attracted people's interest as negative electrodes for lithium-ion batteries due to their high lithium storage capacity and low reaction potential. Ge can react with lithium to produce LiGe alloy at around 0.4V, but since the product after complete lithiation is amorphous, it is difficult to identify whether the product is a 1:1 LiGe alloy; Pb can also react with lithium to form a series of alloying reactions, but since Pb is a heavy metal, it is polluting to the environment; As can react with lithium to form Li3As alloy, but As is very toxic and cannot be used in practice. Among them, two-dimensional layered materials, which are interwoven with anion sheets and cation layers, have also been the subject of research by the scientific community and the chemical industry. BiOCl is such a candidate material with a layered tetragonal crystal structure: it consists of two sheets of chloride ions alternately stacked along the c-axis [Bi2O2] 2+ The structure is composed of sheets. This structure can provide a fast diffusion path along the ion layer and between the ion layers. In addition, the layered structure can provide a large space for the insertion and extraction of lithium atoms. Bi can also form Li3Bi alloy with lithium. However, due to the large atomic mass of Bi, its theoretical specific capacity is low and the content of bismuth in the earth's crust is low (0.5-1.0mmol / kg), which makes it a relatively rare element. Compared with Bi, Fe has the highest annual output of metal-iron (Fe). 3+ The ionic radius Bi 3+ Small enough to create an open volume within the ion layer so that Li + Moreover, S can be used as an active material because it can form Li2S with lithium and undergo a reversible electrochemical reaction. Its reaction potential is relatively high, at 2.4V (vs. Li / Li +), and has a high specific capacity (1163mAh / g). At the same time, Fe nanoparticles can also improve the conductivity of Li2S. Therefore, by introducing iron and sulfur elements into alloy materials, it can not only alleviate the energy scarcity problem of precious metals, but also be an effective way to further improve the coulombic efficiency and capacity of batteries. Summary of the invention

[0003] The present invention aims to find a preparation process, which involves a quasi-spherical iron chlorosulfide lithium-ion battery negative electrode material to improve the performance of lithium-ion batteries. As a solution, the present invention provides a preparation method, which is prepared by mixing ferric chloride with sodium sulfide or thioacetamide at high pressure and high temperature. The quasi-spherical iron chlorosulfide lithium-ion battery negative electrode material has a first efficiency of up to 77% at a current density of 0.2A / g, and the first cycle discharge specific capacity reaches 1554mAh / g.

[0004] 1. A method for preparing a spherical iron chlorosulfide lithium ion battery negative electrode material, comprising the following steps:

[0005] 1. Mix ferric chloride and sodium sulfide or thioacetamide in water at a molar ratio of 1:1 to 1:6, then add a certain amount of surfactant polyethylene glycol 2000, stir with a magnetic stirrer at a speed of 50 to 500 r / min for 10 to 60 min, the concentration of ferric chloride solution is 0.001 to 10 mol / L, the concentration of sodium sulfide or thioacetamide solution is 0.001 to 10 mol / L, and the amount of polyethylene glycol 2000 added is 0.001 to 10 g / L;

[0006] 2. Place the mixed solution of step 1 into an autoclave, heat to 80-250°C, and keep warm for 10-30 hours;

[0007] 3. Wash the product of step 2 with anhydrous ethanol and deionized water successively until the pH value is 5 to 9;

[0008] Fourth, the product obtained in step 3 is placed in a vacuum drying oven and kept at 50-100° C. for 8-20 hours to obtain a spherical iron chlorosulfide lithium-ion battery negative electrode material.

[0009] The preparation method has the advantages of simple operation, low cost and high repeatability. The obtained spherical iron chlorosulfide lithium-ion battery negative electrode material solves the problems of traditional alloy lithium-ion battery negative electrode materials such as small resource storage, high price, low theoretical specific capacity and high toxicity.

[0010] The preparation method is simple to operate, has low preparation cost, and has excellent repeatability, and can stably produce products with consistent performance. The obtained spherical iron chlorosulfide lithium ion battery negative electrode material has a high Fe 3+ Smaller ionic radius can create open volume within the ion layer to facilitate the+ It diffuses faster during the embedding / de-embedding process. And S can be used as an active material because it can form Li2S with lithium, undergoing a reversible electrochemical reaction and improving the battery's specific capacity. At the same time, Fe nanoparticles can also improve the conductivity of Li2S and thus improve the battery's coulombic efficiency. The spherical iron chlorosulfide lithium-ion battery negative electrode material prepared by this method effectively solves the problems of low coulombic efficiency and low capacity existing in traditional graphite negative electrode materials and alloy negative electrode materials. The negative electrode material prepared by this method has shown significant advantages in improving the coulombic efficiency and charge-discharge specific capacity of lithium-ion batteries, significantly improving the economy, practicality and environmental protection of lithium-ion battery production. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a scanning electron microscope photo of the spherical iron chlorosulfide lithium-ion battery negative electrode material prepared in Experiment 1;

[0012] Figure 2 This is the first cycle charge and discharge curve of the spherical iron chlorosulfide lithium-ion battery negative electrode material prepared in Experiment 1;

[0013] Figure 3 This is the cycle diagram of the spherical iron chlorosulfide lithium-ion battery negative electrode material prepared in Experiment 1 at a current density of 0.2A / g. DETAILED DESCRIPTION

[0014] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any combination of the specific implementation modes.

[0015] Specific implementation method 1: A method for preparing a spherical iron chlorosulfide lithium ion battery negative electrode material is carried out according to the following steps:

[0016] 1. Mix ferric chloride and sodium sulfide or thioacetamide in water at a molar ratio of 1:1 to 1:6, then add a certain amount of surfactant polyethylene glycol 2000, stir with a magnetic stirrer at a speed of 50 to 500 r / min for 10 to 60 min, the concentration of ferric chloride solution is 0.001 to 10 mol / L, the concentration of sodium sulfide or thioacetamide solution is 0.001 to 10 mol / L, and the amount of polyethylene glycol 2000 added is 0.001 to 10 g / L;

[0017] 2. Place the mixed solution of step 1 into an autoclave, heat to 80-250°C, and keep warm for 10-30 hours;

[0018] 3. Wash the product of step 2 with anhydrous ethanol and deionized water successively until the pH value is 5 to 9;

[0019] Fourth, the product obtained in step 3 is placed in a vacuum drying oven and kept at 50-100° C. for 8-20 hours to obtain a spherical iron chlorosulfide lithium-ion battery negative electrode material.

[0020] Specific embodiment 2: This embodiment is different from specific embodiment 1 in that the sulfiding agent in step 1 can be selected from sodium sulfide or thioacetamide, the molar ratio of ferric chloride to the sulfiding agent is 1:2 to 1:5, the speed of the magnetic stirrer is controlled at 100 to 400 r / min, the stirring time is maintained at 20 to 50 min, the concentration of ferric chloride solution is 0.01 to 1 mol / L, the concentration of sodium sulfide or thioacetamide solution is 0.01 to 1 mol / L, and the addition amount of polyethylene glycol 2000 is 0.01 to 1 g / L.

[0021] Specific implementation method three: This implementation method is different from specific implementation methods one to two in that the heating temperature in step two is controlled at 100-220° C. and the insulation time is maintained at 15-25 hours.

[0022] Specific implementation method 4: This implementation method is different from specific implementation methods 1 to 3 in that the pH value in step 3 is controlled to be 6-8.

[0023] Specific implementation method 5: This implementation method is different from specific implementation methods 1 to 4 in that the temperature in the vacuum drying oven in step 4 is controlled at 65 to 85° C. and the insulation time is controlled at 10 to 18 hours.

[0024] The following experiments were used to verify the effect of the present invention:

[0025] Experiment 1:

[0026] Preparation method of a spherical iron chlorosulfide lithium ion battery negative electrode material and product performance test:

[0027] 1. Mix 0.16g ferric chloride and 0.25g sodium sulfide in 120ml water, then add 0.01g polyethylene glycol 2000 and stir with a magnetic stirrer at 300r / min for 30min;

[0028] 2. Place the mixed solution of step 1 into an autoclave, heat to 200°C, and keep warm for 12 hours;

[0029] 3. Wash the product of step 2 with anhydrous ethanol and deionized water successively until the pH value is 6;

[0030] 4. The product obtained in step 3 is placed in a vacuum drying oven and kept at 80° C. for 15 h to obtain a spherical iron chlorosulfide lithium-ion battery negative electrode material.

[0031] Product performance test:

[0032] 1. The iron chlorosulfide lithium-ion battery negative electrode material prepared in Experiment 1 was uniformly mixed with the conductive agent acetylene black and the binder PVDF in a mass ratio of 8:1:1, and a solvent N-methylpyrrolidone was added to prepare a slurry, and the slurry was coated on a copper foil to obtain an electrode sheet;

[0033] 2. Place the electrode sheet in a vacuum drying oven and dry it at 90°C for 12 hours. After the electrode sheet is completely dry, punch it into a circular electrode sheet with a diameter of 14 mm.

[0034] 3. The obtained circular electrode sheet was used as the negative electrode, the metal lithium sheet was used as the positive electrode, GradeGF / A was used as the separator, and the electrolyte formula was EC / DMC (1:1)-LiPF6 (1M), and the battery was assembled in a box;

[0035] 4. Use the Blue CT3002A battery test system to perform constant current charge and discharge tests in the voltage range of 0.01 to 3 V. The electrochemical test results show that the first cycle discharge capacity reaches 1554 mAh / g at a current density of 0.2 A / g, and the first cycle coulomb efficiency is as high as 77%.

[0036] Experiment 2:

[0037] A method for preparing a spherical iron chlorosulfide lithium ion battery negative electrode material is carried out according to the following steps:

[0038] 1. Mix 0.35g ferric chloride and 0.6g sodium sulfide in 100ml water, then add 0.05g polyethylene glycol 2000 and stir with a magnetic stirrer at 400r / min for 20min;

[0039] 2. Place the mixed solution of step 1 into an autoclave, heat to 250°C, and keep warm for 15 hours;

[0040] 3. Wash the product of step 2 with anhydrous ethanol and deionized water successively until the pH value is 7;

[0041] Fourth, the product obtained in step 3 is placed in a vacuum drying oven and kept at 100° C. for 10 h to obtain a spherical iron chlorosulfide lithium-ion battery negative electrode material.

Claims

1. A method for preparing a spherical iron chlorosulfide lithium ion battery negative electrode material, comprising the steps of:

1. Mix ferric chloride and sodium sulfide or thioacetamide in water at a molar ratio of 1:1 to 1:6, then add a certain amount of surfactant polyethylene glycol 2000, stir with a magnetic stirrer at a speed of 50 to 500 r / min for 10 to 60 min, the concentration of ferric chloride solution is 0.001 to 10 mol / L, the concentration of sodium sulfide or thioacetamide solution is 0.001 to 10 mol / L, and the amount of polyethylene glycol 2000 added is 0.001 to 10 g / L; 2. Place the mixed solution of step 1 into an autoclave, heat to 80-250°C, and keep warm for 10-30 hours; 3. Wash the product of step 2 with anhydrous ethanol and deionized water successively until the pH value is 5 to 9; Fourth, the product obtained in step 3 is placed in a vacuum drying oven and kept at 50-100° C. for 8-20 hours to obtain a spherical iron chlorosulfide lithium-ion battery negative electrode material.

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