A layered sulfide LiVS2 anode material for lithium-ion batteries

Abstract

This invention belongs to the field of anode materials and provides a layered sulfide LiVS2 anode material for lithium-ion batteries. The method includes: mixing, grinding, and pressing Li2S powder, V powder, and S powder to obtain thin sheets; and then using chemical vapor deposition to fabricate single-crystal LiVS2 from the thin sheets. The mass ratio of Li2S powder, V powder, and S powder is 1–2:2–4:3–6. Compared with existing LiVS2 materials, this invention successfully synthesizes single-crystal LiVS2 with a layered structure through chemical vapor deposition, effectively improving its rate performance and cycle performance.

Description

Technical Field

[0001] This invention belongs to the field of anode materials, and specifically relates to a layered sulfide LiVS2 anode material for lithium-ion batteries. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] In recent years, the electric vehicle market has developed rapidly, and lithium-ion batteries, as a crucial component of current electric vehicles, require continuous innovation and progress in their technological field. Currently, commercially available graphite anode materials suffer from slow reaction kinetics, making them unsuitable for high-rate applications, and the formation of lithium dendrites can easily cause safety issues. Spinel-type Li₄Ti₅O₃ is being considered as an alternative material. 12 It exhibits high structural stability and safety, but its theoretical specific capacity (175 mAh g) is relatively low. -1 ) and a higher charge / discharge plateau (≈1.55V versus Li + The presence of Li₂O₃ limits its further applications. Therefore, it is necessary to continuously explore new anode materials to overcome the shortcomings of traditional materials and comprehensively improve the performance of lithium-ion batteries. The paper "Mechanochemical Synthesis and Electrochemical Properties of Li₂O₃" addresses this. x VS y The paper "Positive Electrodes for All-Solid-State Batteries" discloses a Li-based solid-state battery. x VS y It is a cathode material, but its electrochemical performance still needs to be improved. Summary of the Invention

[0004] To address the aforementioned issues, this invention successfully synthesizes single-crystal LiVS2 with a layered structure by mixing Li2S powder, V powder, and S powder to form thin sheets, followed by chemical vapor deposition. This effectively improves its rate performance and cycle performance, and its electrochemical performance is investigated as a negative electrode material for lithium-ion batteries.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A first aspect of the present invention provides a layered sulfide LiVS2 anode material for lithium-ion batteries, comprising:

[0007] Li2S powder, V powder, and S powder are mixed, ground, and compressed into tablets to obtain thin sheets.

[0008] The thin film was fabricated into single-crystal LiVS2 using chemical vapor deposition.

[0009] The mass ratio of Li2S powder, V powder, and S powder is 1-2:2-4:3-6.

[0010] This invention synthesizes LiVS2 through a specific process and applies it as a negative electrode material for lithium-ion batteries. As a relatively novel material, it is subjected to charge-discharge tests in two potential ranges (0.9-1.8V, 1.8-2.6V) to explore its electrochemical performance in the two ranges.

[0011] In some embodiments, the grinding time is 10-40 min.

[0012] In some embodiments, the specific step of tableting is to pour the mixed powder into a tableting mold and press it into a thin sheet.

[0013] In some embodiments, the specific steps of the chemical vapor deposition method are as follows: loading a thin film into a quartz tube, sealing it under vacuum, then calcining it and cooling it to room temperature.

[0014] In some embodiments, the calcination temperature of the chemical vapor deposition method is 650-900°C.

[0015] In some embodiments, the holding time for the chemical vapor deposition method is 24-72 hours.

[0016] In some embodiments, the temperature is increased to 650-900°C at a rate of 0.5-5°C / min.

[0017] In a second aspect, the present invention provides a layered sulfide LiVS2 anode material for lithium-ion batteries prepared by the above-described method.

[0018] In some embodiments, the grain size is 1 to 10 μm, and the grain is formed by the stacking of many lamellar grains.

[0019] A third aspect of the present invention provides a lithium-ion battery, wherein the negative electrode material is the aforementioned LiVS2 negative electrode material.

[0020] Beneficial effects of the present invention

[0021] (1) Compared with existing LiVS2, the present invention successfully synthesizes single-crystal LiVS2 with a layered structure by chemical vapor deposition, which effectively improves its rate performance and cycling performance, as follows:

[0022] Within the potential range of 0.9-1.8V: at 0.1Ag -1The discharge specific capacity of LiVS2 at a current density of approximately 179.5 mAh g -1 At a high current density of 3.2Ag -1 The discharge specific capacity is approximately 98.0 mAh g. -1 0.2Ag -1 The discharge specific capacity after 100 cycles at the specified current density is 98.5 mAh g. -1 The capacity retention rate was approximately 58.7%. 0.6Ag -1 The discharge specific capacity after 300 (100) cycles at the given current density is 57.1 mAh g. -1 The capacity retention rate was approximately 37.6% (70.7%).

[0023] Within the potential range of 1.8-2.6V: at 0.1Ag -1 The discharge specific capacity of LiVS2 at a current density of approximately 201.6 mAh g -1 At a high current density of 3.2Ag -1 The discharge specific capacity is approximately 104.7 mAh g. -1 0.2Ag -1 The discharge specific capacity after 100 cycles at a current density is 171.6 mAh g. -1 The capacity retention rate is approximately 96.8%. 0.6Ag -1 The discharge specific capacity after 300 (100) cycles at the given current density is 103.0 mAh g. -1 The capacity retention rate was approximately 62.6% (84.4%).

[0024] The results above show that LiVS2 has excellent rate performance in the potential ranges of 0.9-1.8V and 1.8-2.6V, and good cycling performance in the potential range of 1.8-2.6V.

[0025] (2) The preparation method of the present invention is simple, practical and easy to promote. Attached Figure Description

[0026] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0027] Figure 1 XRD pattern of LiVS2;

[0028] Figure 2 SEM images of LiVS2 samples at magnifications of 5K(a) and 10K(b);

[0029] Figure 3TEM image (a) and SAED image (b) of the LiVS2 sample;

[0030] Figure 4 The constant current charge-discharge voltage curves (a) and CV curves (b) of the LiVS2 sample are shown.

[0031] Figure 5 For comparison of electrochemical performance. (a) Rate performance of LiVS2 sample in two voltage ranges; (b, c) Cycling performance of LiVS2 sample at different current densities in two voltage ranges. Detailed Implementation

[0032] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0033] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0034] Example 1

[0035] Weigh a certain amount of Li2S powder, V powder, and S powder in a ratio of 1:2:3, mix and grind them in a mortar for 25 minutes, then pour the evenly mixed powder into a pressing mold to press it into a thin sheet. After demolding, the sample sheet is placed into a quartz tube, taken out of the glove box, and quickly vacuum-sealed. The sealed quartz tube is then placed in a muffle furnace and heated to 800℃ at a rate of 2.5℃ / min. After holding at this temperature for 48 hours, it is slowly cooled to room temperature with the furnace to finally obtain single crystal LiVS2.

[0036] The crystal structure of the sample prepared in this embodiment was tested by X-ray diffraction pattern, corresponding to JCPDS card number 72-0863. No other impurity phases were found. Figure 1 As shown, this experimental method yields a LiVS2 sample with high purity.

[0037] like Figure 2 As shown, the morphology of LiVS2 was characterized by SEM. Figure 2 In (a), it can be observed that the sample as a whole is composed of grains of different sizes, with a grain size of approximately 1–10 μm. Figure 2 (b) is a Figure 2 The magnified view of a local area in (a) at 10K magnification shows more clearly that the larger grains are composed of many lamellar grains stacked together.

[0038] like Figure 3As shown, the TEM results reveal the layered structure of LiVS2. The SAED diffraction pattern clearly shows that the LiVS2 sample has a single-crystal structure and identifies the

[101] zone band. . crystal facets.

[0039] Example 2

[0040] (1) Electrode preparation

[0041] The negative electrode active material (LiVS2), conductive agent (carbon black Super-P), and binder (CMC) prepared in Example 1 were weighed at a mass ratio of 8:1:1, dried, and thoroughly ground in a mortar. After mixing evenly, the mixture was placed in a weighing bottle. An appropriate amount of N-methylpyrrolidone (NMP) solution was added, and the weighing bottle was placed in an automatic stirring device and stirred for a certain period of time to obtain a well-mixed slurry. The well-mixed slurry was coated onto a pre-cut 14 mm copper foil and vacuum dried at 80 °C for 12 h. The dried active material and copper foil were then cut into circular electrode sheets with a diameter of 14 mm using a stamping machine and placed in a glove box for later use. Because the LiVS2 sample is very sensitive to air, the electrode preparation must be carried out entirely in a glove box.

[0042] (2) Assembly of button batteries

[0043] The button cell batteries were assembled in an argon-filled glove box, where the oxygen and water content were both less than 0.1 ppm. This experiment used a CR2032 battery case for reverse assembly. The electrolyte was a 1M lithium hexafluorophosphate (LiPF6) solution dissolved in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) (volume ratio 1:1:1). A Celgard 2500 polypropylene membrane was used as the separator. First, a 0.5mm stainless steel gasket and electrode plates were placed sequentially into the negative electrode case. An appropriate amount of electrolyte was dripped onto the electrode plates, and then the separator was placed in place. The counter electrode (lithium sheet) and stainless steel gasket were then placed in sequence. Air bubbles were gently pressed out of the gasket with tweezers, and a spring gasket was placed in place. The positive electrode case was then placed on top of the negative electrode case, and the battery was packaged in a button cell battery packaging machine. To ensure the electrolyte fully wetted the separator and electrodes, all assembled button cells were allowed to stand for 6 hours before testing.

[0044] like Figure 4 As shown, Figure 4 In Figure (a) and (b), the constant current charge-discharge voltage curves and CV curves of the LiVS2 sample during the 2nd, 3rd, and 5th cycles in the 0.8–2.6 V range are shown, respectively. Figure 4As shown in (a), the sample exhibits charge-discharge plateaus around 2.2V and 1.1V, corresponding to the conversion reactions between VS2 and LiVS2, and between LiVS2 and Li2VS2, respectively. Simultaneously, the two pairs of redox peaks in the CV curve are also located around 2.2V and 1.1V, with the redox peak around 2.2V corresponding to V... 4+ and V 3+ The conversion reaction between them, the redox peak at around 1.1V corresponds to V 3+ and V 2+ The conversion reaction between them is the same as the result of the charge-discharge voltage curve.

[0045] Figure 5 Figure (a) shows the rate performance at different current densities in two voltage ranges. In the 0.9–1.8 V range, at 0.1 Ag... -1 0.2Ag -1 0.4Ag -1 0.8Ag -1 1.6Ag -1 2.4Ag -1 3.2Ag -1 The average specific capacities of the LiVS2 samples at the given current densities were 179.5, 168.2, 159.1, 148.5, 130.7, 113.9, and 98.0 mAh g, respectively. -1 When the current density recovers to 0.1 Ag -1 The specific capacity recovered to approximately 162.5 mAh g. -1 Within the 1.8-2.6V range, at 0.1Ag -1 0.2Ag -1 0.4Ag -1 0.8Ag -1 1.6Ag -1 2.4Ag -1 3.2Ag -1 The average specific capacities of the LiVS2 samples at the given current densities were 201.6, 195.5, 182.2, 163.6, 140.7, 119.9, and 103.1 mAh g⁻¹. -1 When the current density recovers to 0.1 Ag -1 The specific capacity recovered to approximately 201.4 mAh g. -1 Because the capacity decay is significant with each cycle in the 0.9-1.8V range, 0.1Ag is selected. -1 Specific capacity after ten cycles (173.8 mAh g) -1 For reference, at a high current density of 3.2Ag -1 The capacity retention rate is approximately 56.4% at the lower voltage range, which is higher than 51.1% in the 1.8-2.6V range.

[0046] Figure 5 (b) shows the concentration of 0.2Ag -1 Cycling performance at low current densities in two voltage ranges: after 100 cycles, the specific capacity of the sample increased from 167.8 mAh g / L in the 0.9–1.8 V voltage range. -1 Reduced to 98.5mAhg -1 It exhibits a capacity retention of 58.7%. The specific capacity of the sample ranges from 177.2 mAh g / g in the 1.8–2.6 V voltage range. -1 Reduced to 171.6mAhg -1 It has a capacity retention rate of 96.8%. Figure 5 (c) represents 0.6Ag -1 Cycling performance diagrams for two voltage ranges at higher current densities. After 300 cycles in the 0.9–1.8 V voltage range, the specific capacity of the sample increased from 151.7 mAh g / g. -1 Reduced to 57.1 mAhg -1 It exhibits a capacity retention of 37.6%. The specific capacity of the sample ranges from 164.6 mAh g / g in the 1.8–2.6 V voltage range. -1 Reduced to 103.0 mAhg -1 It exhibits a capacity retention of 96.8%. The capacity retention is approximately 62.6%. It is noteworthy that at 0.6 Ag... -1 After 100 cycles at current density, the mass retention is approximately 70.7% in the 0.9–1.8 V range, which is higher than that at 0.2 Ag. -1 (58.7%).

[0047] Electrochemical performance comparison reveals that LiVS2 exhibits superior rate performance in the potential ranges of 0.9-1.8V and 1.8-2.6V (with better rate performance in the 0.9-1.8V range), good cycling performance in the 1.8-2.6V range, and poor cycling performance in the 0.9-1.8V range.

[0048] Example 3

[0049] Weigh a certain amount of Li2S powder, V powder, and S powder in a ratio of 1:2:3, mix and grind them in a mortar for 10 minutes, then pour the evenly mixed powder into a pressing mold to press it into a thin sheet. After demolding, the sample sheet is placed into a quartz tube, taken out of the glove box, and quickly vacuum-sealed. The sealed quartz tube is then placed in a muffle furnace and heated to 900℃ at a rate of 5℃ / min. After holding at this temperature for 24 hours, it is slowly cooled to room temperature with the furnace to finally obtain single crystal LiVS2.

[0050] Example 4

[0051] Weigh a certain amount of Li2S powder, V powder, and S powder in a ratio of 1:2:3, mix and grind them in a mortar for 40 minutes, then pour the uniformly mixed powder into a pressing mold to press it into a thin sheet. After demolding, the sample sheet is placed into a quartz tube, taken out of the glove box, and quickly vacuum-sealed. The sealed quartz tube is then placed in a muffle furnace and heated to 650℃ at a rate of 0.5℃ / min. After holding at this temperature for 72 hours, it is slowly cooled to room temperature with the furnace to finally obtain single crystal LiVS2.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a layered sulfide LiVS2 anode material for lithium-ion batteries, characterized in that, include: Li2S powder, V powder, and S powder are mixed, ground, and compressed into tablets to obtain thin sheets. The thin film was fabricated into single-crystal LiVS2 using chemical vapor deposition. The mass ratio of Li2S powder, V powder, and S powder is 1~2:2~4:3~6. The specific steps of the chemical vapor deposition method are as follows: the thin film is loaded into a quartz tube, vacuum sealed, then calcined and cooled to room temperature.

2. The method for preparing the layered sulfide LiVS2 anode material for lithium-ion batteries as described in claim 1, characterized in that, The grinding time is 10-40 minutes.

3. The method for preparing the layered sulfide LiVS2 anode material for lithium-ion batteries as described in claim 1, characterized in that, The specific steps of tableting are to pour the mixed powder into a tableting mold and press it into a thin sheet.

4. The method for preparing the layered sulfide LiVS2 anode material for lithium-ion batteries as described in claim 1, characterized in that, The calcination temperature for the chemical vapor deposition method is 650-900℃.

5. The method for preparing the layered sulfide LiVS2 anode material for lithium-ion batteries as described in claim 1, characterized in that, The holding time for the chemical vapor deposition method is 24-72 hours.

6. The method for preparing the layered sulfide LiVS2 anode material for lithium-ion batteries as described in claim 4, characterized in that, Heating to 650-900℃ at a rate of 0.5-5℃ / min.

7. The layered sulfide LiVS2 anode material for lithium-ion batteries prepared by the method according to any one of claims 1-6.

8. The LiVS2 anode material as described in claim 7, characterized in that, The grain size is 1~10 μm, and the grain is formed by the stacking of many lamellar grains.

9. A lithium-ion battery, characterized in that, The negative electrode material is the LiVS2 negative electrode material as described in claim 7 or 8.

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