TiS2 negative electrode material for rapid charging of lithium ion batteries

Abstract

The application belongs to the field of lithium batteries, and provides a TiS2 negative electrode material for rapid charging of a lithium ion battery, which comprises the following steps: uniformly mixing titanium powder and sulfur powder to form a flake; and using a gas phase chemical deposition method to form single-crystal multi-dislocation titanium disulfide from the flake. The single-crystal structure can improve the charge and discharge rate capacity by reducing the grain boundaries of the lithium ion diffusion path, the structure characteristics of the multi-dislocation can buffer the volume expansion in the charge and discharge process, reduce the diffusion distance of ions and electrons to meet the requirement of rapid charge and discharge, and the dislocation defects can increase the lithium storage active sites, and improve the reversible capacity and rate performance of the material.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of lithium batteries, and particularly relates to a TiS2 negative electrode material for fast charging of lithium ion batteries. BACKGROUND

[0002] The information disclosed in this Background section is for the purpose of increasing an understanding of the general context of the present application and is not necessarily recognized as prior art against the present application.

[0003] Automotive electrification has become a trend in the future development of the automotive industry. However, the short driving range and long charging time hinder the further expansion of the electric vehicle market. Therefore, there is a need for a fast-charging electrode material that meets the demand for fast charging of batteries while ensuring high energy density and safety. Spinel lithium titanate (Li4Ti5O 12 , LTO) negative electrode material has been widely and deeply concerned and researched in the field of lithium ion battery fast charging due to its "zero strain" characteristics and high safety. However, the theoretical specific capacity (175 mAhg -1 ) of the spinel lithium titanate material is relatively low, which limits its practical application in the battery field. For example: the paper "TiS2 as an Advanced Conversion Electrode for Sodium-Ion Batteries with Ultra-High Capacity and Long-Cycle Life" first applied titanium disulfide (TiS2) as a conversion reaction negative electrode material in sodium ion batteries. The preparation method includes: titanium disulfide samples (TiS2) were prepared by high-temperature vacuum sintering method, but the application of TiS2 in lithium ion batteries was not disclosed, and its cycle performance and rate performance need to be improved.

[0004] Transition metal sulfide titanium disulfide (TiS2) has good application prospects in the application of lithium ion battery negative electrode materials due to its superior layered structure, good lithium intercalation performance and high theoretical specific capacity.

[0005] Therefore, there is an urgent need to develop a lithium ion battery negative electrode material that meets the demand for fast charging of batteries while ensuring high energy density and safety. SUMMARY

[0006] In order to meet the demand of fast charging of the battery under the condition of ensuring high energy density and safety, the titanium powder and the sulfur powder are made into flakes, and single crystal and multi-dislocation titanium disulfide (TiS2) is synthesized by using a gas phase chemical deposition method for a lithium ion battery negative electrode material, the single crystal structure can reduce the grain boundary of the lithium ion diffusion path to improve the charge and discharge rate capacity, the multi-dislocation structure characteristics can buffer the volume expansion in the charging and discharging process, reduce the diffusion distance of ions and electrons to meet the demand of fast charging, and the dislocation defects can increase the lithium storage active sites, and improve the reversible capacity and rate performance of the material.

[0007] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0008] In a first aspect, the present application provides a TiS2 negative electrode material for fast charging of a lithium ion battery, comprising:

[0009] The titanium powder and the sulfur powder are mixed uniformly to make flakes;

[0010] The flakes are made into single crystal and multi-dislocation titanium disulfide by using a gas phase chemical deposition method.

[0011] The titanium powder and the sulfur powder are made into flakes, and single crystal and multi-dislocation titanium disulfide (TiS2) is synthesized by using a gas phase chemical deposition method for a lithium ion battery negative electrode material, the single crystal structure can reduce the grain boundary of the lithium ion diffusion path to improve the charge and discharge rate capacity, the multi-dislocation structure characteristics can buffer the volume expansion in the charging and discharging process, reduce the diffusion distance of ions and electrons to meet the demand of fast charging, and the dislocation defects can increase the lithium storage active sites, and improve the reversible capacity and rate performance of the material.

[0012] In some embodiments, the mass ratio of the titanium powder and the sulfur powder is 1-3:2-6.

[0013] In some embodiments, the specific method of mixing is to grind the titanium powder and the sulfur powder together for 10-30 minutes.

[0014] In some embodiments, the specific steps of the gas phase chemical deposition method are to load the flakes into a container, vacuum seal, calcine, and cool to room temperature.

[0015] In some embodiments, the calcination temperature is 640-650 DEG C.

[0016] In some embodiments, the holding time is 24-72 hours.

[0017] In some embodiments, the heating rate is 1-5 DEG C / min.

[0018] In a second aspect, the present application provides a TiS2 negative electrode material prepared by the above-mentioned method.

[0019] In some embodiments, the TiS2 negative electrode material is in a nanosheet morphology, is hexagonal in shape, has a lateral dimension of 1-5 μm, and has a thickness of less than 500 nm.

[0020] In a third aspect, the application provides a lithium ion battery, the negative electrode material of which is the TiS2 negative electrode material described above.

[0021] Advantages of the application

[0022] (1) The SD-TiS2 of the application has a specific discharge capacity of about 236.7 mAhg-1 at a current density of 0.05 Ag-1, a specific discharge capacity of about 177.4 mAhg-1 at a high current density of 3.2 Ag-1, which is much higher than that of commercial TiS2 (about 103.0 mAhg-1) and also higher than the theoretical specific capacity of common fast-charging material Li4Ti5O12 (175 mAhg-1), and a high specific discharge capacity of about 157.7 mAhg-1 even at an ultra-high current density of 6.4 Ag-1. -1 -1 -1 -1 -1 12 -1 -1 -1 -1 -1 -1 -1 -1 -1

[0023] (2) The application uses titanium powder and sulfur powder to form a thin sheet, and uses a gas-phase chemical deposition method to synthesize single-crystal and multi-dislocation titanium disulfide (TiS2) for use as a lithium ion battery negative electrode material. The single-crystal structure can improve the charge and discharge rate capability by reducing the grain boundaries of the lithium ion diffusion path, the multi-dislocation structure can buffer the volume expansion during the charge and discharge process, reduce the diffusion distance of ions and electrons to meet the requirement of fast charge and discharge, and the dislocation defects can increase the lithium storage active sites to improve the reversible capacity and rate performance of the material.

[0024] (3) The preparation method of the application is simple, practical, and easy to popularize. BRIEF DESCRIPTION OF DRAWINGS ​​​​​​​​​​​​​​​

[0025] The accompanying drawings, which form a part of this specification, are included to provide a further understanding of the application, and are incorporated into and constitute a part of this specification. The embodiments of the application, and their

[0026] Figure 1 are XRD patterns of SD-TiS2 and Com-TiS2;

[0027] Figure 2 are SEM images of SD-TiS2 (a, b) and Com-TiS2 (c, d) at 5K and 10K magnification;

[0028] Figure 3 are TEM images of SD-TiS2 (a) and Com-TiS2 (b), SAED images of SD-TiS2 (c) and Com-TiS2 (d);

[0029] Figure 4 are Raman spectrum of SD-TiS2 (a) and XPS fine spectrum of Ti 2p (b);

[0030] Figure 5 are electrochemical performance comparisons. (a) Rate performance of two TiS2 samples; (b, c) cycle performance of two TiS2 samples at different current densities;

[0031] Figure 6 are (a) CV curves of SD-TiS2 electrode between 1-3 V at a scan rate of 0.1 mV s -1 (b) Electrochemical impedance spectra of two TiS2 samples (inset: corresponding simulated equivalent circuit diagram). DETAILED DESCRIPTION

[0032] It should be noted that the following detailed description is merely exemplary and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0033] The application will be described in further detail with reference to specific embodiments. It should be noted that the specific embodiments are illustrative of the application and are not intended to be limiting.

[0034] In the following examples, Com-TiS2 is a commercial titanium disulfide purchased from Beijing InoKai Technology Co., Ltd., and has a morphology of large blocks.

[0035] Example 1

[0036] Take 0.2 g of Ti powder and 0.42 g of S powder (S excess), mix and grind in a mortar for 20 minutes, then pour the uniformly mixed powder into a tablet press mold to press into a thin sheet, and then put the sample sheet after demolding into a quartz tube. After taking it out of the glove box, it is quickly vacuum sealed, and the sealed quartz tube is placed in a muffle furnace to heat to 650°C at a rate of 2.5°C / min, and slowly cooled to room temperature after 48h of heat preservation. Finally, single-crystal multi-dislocation titanium disulfide (SD-TiS2) is obtained. (Commercial titanium disulfide is represented by Com-TiS2).

[0037] Example 2

[0038] Take 0.1 g of Ti powder and 0.22 g of S powder (S excess), mix and grind in a mortar for 10 minutes, then pour the uniformly mixed powder into a tablet press mold to press into a thin sheet, and then put the sample sheet after demolding into a quartz tube. After taking it out of the glove box, it is quickly vacuum sealed, and the sealed quartz tube is placed in a muffle furnace to heat to 640°C at a rate of 1°C / min, and slowly cooled to room temperature after 72h of heat preservation. Finally, single-crystal multi-dislocation titanium disulfide is obtained.

[0039] Example 3

[0040] Take 0.3 g of Ti powder and 0.64 g of S powder (S excess), mix and grind in a mortar for 30 minutes, then pour the uniformly mixed powder into a tablet press mold to press into a thin sheet, and then put the sample sheet after demolding into a quartz tube. After taking it out of the glove box, it is quickly vacuum sealed, and the sealed quartz tube is placed in a muffle furnace to heat to 650°C at a rate of 5°C / min, and slowly cooled to room temperature after 24h of heat preservation. Finally, single-crystal multi-dislocation titanium disulfide is obtained.

[0041] Example 4

[0042] (1) Preparation of electrode

[0043] The negative active material (SD-TiS2 prepared in Example 1 and commercially available Com-TiS2), conductive agent (carbon black Super-P) and binder (CMC) are weighed in a mass ratio of 8:1:1 after drying, and then thoroughly ground in a mortar. After mixing uniformly, it is placed in a weighing bottle. After adding an appropriate amount of N-methyl pyrrolidone (NMP) solution, the weighing bottle is placed in an automatic stirring device for a certain period of time to obtain a mixed slurry. The mixed slurry is coated on a 14 mm copper foil cut in advance, and vacuum dried at 80°C for 12h. The dried active material and copper foil are cut into circular electrode sheets with a diameter of 14 mm using a sheet puncher, and then placed in a glove box for use. The preparation of the electrode needs to be carried out in the glove box throughout the process.

[0044] (2) Assembly of button cell

[0045] 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.

[0046] The crystal structures of SD-TiS2 and Com-TiS2 prepared in Example 1 were tested by X-ray diffraction patterns. The JCPDS card numbers of the two samples were 88-1967 and 74-1141, respectively. No other impurities were found, indicating that the experimental method prepared high-purity TiS2 samples.

[0047] Figure 2 The images show SEM images of SD-TiS2 (a,b) and Com-TiS2 (c,d) at magnifications of 5K and 10K. The SEM results indicate that the TiS2 samples prepared using the method of this invention exhibit a dispersed nanosheet morphology with a hexagonal shape, a lateral dimension of approximately 1–5 μm, and a thickness of less than 500 nm. In contrast, commercial TiS2 samples tend to form large and thick nanosheets.

[0048] Figure 3 The images show TEM images of SD-TiS2 (a) and Com-TiS2 (b), and SAED images of SD-TiS2 (c) and Com-TiS2 (d). TEM results indicate that the SD-TiS2 sample contains a large number of dislocations compared to Com-TiS2. The clear periodic diffraction spots in the SAED images show that the Com-TiS2 sample has a single-crystal structure and identifies the (010) zone belonging to the

[101] zone. The crystal planes of TiS2 are distinct, while Com-TiS2 exhibits weak polycrystalline diffraction rings, with three of the diffraction rings corresponding to the (010) crystal planes of TiS2. (031) The surfaces match well and both belong to the

[001] crystal zone.

[0049] Figure 4 Raman spectrum (a) of SD-TiS2 and fine XPS spectrum of Ti 2p (b). The Raman spectrum shows that SD-TiS2 reaches a wavenumber of 151.2 cm⁻¹.-1 , 428.2 cm -1 , and 622.0 cm -1 There are three TiS2 characteristic peaks, and no obvious impurity peaks, which proves that the prepared sample is high-purity TiS2. The Ti 2p peaks of SD-TiS2 can be separated into four characteristic peaks with different intensities at 455.8 eV, 458.5 eV, 462.1 eV and 464.6 eV, which correspond to Ti 3+ 2p 2 / 3 , Ti 4+ 2p 2 / 3 , Ti 3+ 2p 1 / 2 , Ti 4+ 2p 1 / 2 , SD-TiS2 has a higher Ti 3+ concentration, indicating that there are many defects on the surface of the sample, which also helps to prove that there are a large number of dislocations in the SD-TiS2 sample.

[0050] Figure 5 Figure (a) in the middle shows the rate performance of the two TiS2 samples at different current densities. It can be seen that SD-TiS2 has the best rate performance, and the average specific capacity at 0.05 Ag -1 , 0.1 Ag -1 , 0.2 Ag -1 , 0.4 Ag -1 , 0.8 Ag -1 , 1.6 Ag -1 , 3.2 Ag -1 current density is 236.7, 228.0, 220.1, 212.2, 203.6, 192.3, 177.4 mAhg -1 , even at a super-high current density of 6.4 Ag -1 , the specific capacity is as high as 157.7 mAhg -1 . When the current density returns to 0.05 Ag -1 , the specific capacity returns to about 230.6 mAhg -1 , with a capacity retention of 97.4%, indicating the high structural stability of SD-TiS2. Figure 5 Figure (b) in the middle shows the cycle performance of the two samples at a low current density of 0.2 Ag -1 , after 200 cycles, the specific capacity of SD-TiS2 decreases from 231.1 mAhg -1 to 216.5 mAhg -1 , with a capacity retention of 93.7%, and the first cycle coulombic efficiency is 89.4%. After cycling under the same conditions, Com-TiS2 only retains 140.0 mAhg -1Its specific capacity is much lower than that of SD-TiS2, while its capacity retention (91.4%) and first-cycle coulombic efficiency (84.8%) are both lower than those of Com-TiS2. At a higher current density of 0.6 Ag... -1 The electrode material SD-TiS2 synthesized in this invention still retains 184.6 mAh g⁻¹ after 300 cycles. -1 Its discharge specific capacity and capacity retention rate are as high as 91.0%, which is also superior to commercial TiS2 (85.6%).

[0051] Depend on Figure 6 The CV curves in (a) reveal two pairs of redox peaks centered at 1.9 V and 2.3 V, respectively, indicating two reversible phase transitions on the surface during electrochemical lithium insertion and extraction. The current density in the first cycle is slightly higher than in subsequent cycles, and the reduction potential shifts slightly, possibly due to side reactions occurring on the electrode surface. In subsequent cycles, the CV curves exhibit remarkably similar shapes and current densities, demonstrating excellent electrochemical and structural stability of the SD-TiS2 surface during lithium-ion insertion and extraction. Figure 6 (b) shows the AC impedance spectra of the two materials, further confirming the superior electrochemical performance of the SD-TiS2 sample. The inset shows the improved Randles-Ershler equivalent circuit. In the Nyquist plot, the semicircles in the high-frequency region correspond to the charge transfer resistance (Rc). ct The sloping straight line in the low-frequency region represents the Weber impedance (Z). w Therefore, it can be seen that the charge transfer resistance of SD-TiS2 is significantly lower than that of Com-TiS2, thus SD-TiS2 has better electrochemical performance.

[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 TiS2 negative material for fast charging of lithium-ion batteries, characterized in that, The application relates to a method for preparing a TiS2 negative electrode material. Titanium powder and sulfur powder are uniformly mixed to prepare a flake; The flake is used to prepare single-crystal multi-dislocation titanium disulfide by a gas phase chemical deposition method, and the titanium disulfide is obtained. The specific steps of the gas phase chemical deposition method are as follows: the flake is loaded into a container, vacuumized and sealed, calcined, and cooled to room temperature, and the titanium disulfide is obtained; the calcination temperature is 640 DEG C to 650 DEG C; and the holding time is 24-72h.

2. The method for preparing TiS2 cathode material for fast charging of lithium ion batteries as claimed in claim 1, wherein, The mass ratio of the titanium powder to the sulfur powder is 1-3:2-6.

3. The method for preparing TiS2 cathode material for fast charging of lithium ion batteries as claimed in claim 1, wherein, The specific method of the mixing is that the titanium powder and the sulfur powder are jointly ground for 10-30min.

4. The method for preparing TiS2 cathode material for fast charging of lithium ion batteries as claimed in claim 1, wherein, The heating rate is 1-5 DEG C / min.

5. The TiS2 negative electrode material prepared by the method in any one of claims 1-4.

6. The TiS2 cathode material of claim 5, wherein, The TiS2 negative electrode material is in a nanosheet shape, is hexagonal in shape, has a lateral size of 1-5 mu m, and has a thickness of less than 500 nm.

7. A lithium-ion battery, characterized by The negative electrode material is the TiS2 negative electrode material in claim 5 or 6.

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