A blue niobium oxide anode material, its preparation method and application in fast-charging lithium-ion batteries

Abstract

The present invention discloses a blue niobium oxide negative electrode material, a preparation method thereof, and an application in a fast-charging lithium-ion battery. Step (1): Weigh Nb2O5 and NbO2, fully mix and grind them on a mixer, and press them into tablets to obtain precursor thin sheets. Step (2): Place the precursor thin sheets obtained in step (1) in a tubular furnace with Ar flowing through for calcination and heat preservation, then cool to room temperature and grind to obtain blue niobium oxide powder. Step (3): Crush and grind the blue niobium oxide powder obtained in step (2) with a mortar, dry it, use it as an active material, mix it with conductive carbon black and polyvinylidene fluoride, and further grind it after adding NMP to prepare a blue niobium oxide negative electrode material. The lithium-ion battery negative electrode material prepared by the present invention has the advantages of good structural stability, good high-rate performance, and good cycle stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of anode materials for lithium-ion batteries, and specifically relates to a blue niobium oxide anode material, a preparation method thereof, and an application in fast-charging lithium-ion batteries. Background Art

[0002] Compared with secondary batteries such as lead-acid batteries and nickel-cadmium batteries, lithium-ion batteries have many advantages as power batteries for electric vehicles, such as high energy density, long cycle life, low self-discharge rate, no memory effect, and good safety. On the premise of ensuring safety and economic benefits, how to further improve the power density and energy density of lithium-ion batteries has become a research hotspot. The key lies in developing high-performance electrode materials.

[0003] For the anode materials in batteries, the currently mainly successfully commercialized ones are graphite (Patent No.: CN201310115596.5, Publication No.: CN103199254A) and lithium titanate anode materials (Patent No.: CN202310054730.9, Publication No.: CN115799486A). Graphite as an anode material has a theoretical capacity of 372 mAh g -1 , and it has advantages such as low price and rich raw materials. However, its lithium intercalation potential is relatively low, its rate performance is poor, and it is easy to form lithium dendrites that pierce the diaphragm, resulting in relatively large safety hazards; lithium titanate, as a "zero-strain material", has high cycle stability and service life, but its theoretical capacity is relatively low, only 175 mAh g -1 .

[0004] In view of the above introduction of the two anode materials, a lithium-ion battery anode material with good structural stability, high lithium intercalation potential, good safety, and relatively high theoretical capacity is needed to achieve high rate performance and cycle stability. Summary of the Invention

[0005] In order to overcome the above technical problems, the purpose of the present invention is to provide a blue niobium oxide anode material, a preparation method thereof, and an application in fast-charging lithium-ion batteries, to overcome the formation of lithium dendrites and volume expansion problems. The lithium-ion battery anode material prepared by this method has the advantages of good structural stability, good high-rate performance, and good cycle stability.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0007] A blue niobium oxide anode material, when observed under a scanning electron microscope, has a short rod-like morphology, the primary particle size is 3 - 5 μm, it is a micron-sized particle, presents a short rod-like shape, and has strong adhesiveness.

[0008] Compared with nanomaterials, their advantages are low production energy consumption, higher tap density, fewer side reactions, smaller volume expansion, and the material structure is not prone to collapse or pulverization.

[0009] A method for preparing a blue niobium oxide negative electrode material comprises the following steps:

[0010] Step (1): weigh Nb2O5 and NbO2, mix and grind them thoroughly on a mixer, and press them into sheets to obtain precursor sheets;

[0011] Step (2): placing the precursor flakes described in step (1) in a tubular furnace filled with Ar for calcination and heat preservation, cooling to room temperature, and grinding to obtain blue niobium oxide powder;

[0012] Step (3): The blue niobium oxide powder obtained in step (2) is crushed and ground with a mortar, dried, and used as an active material. It is mixed with conductive carbon black (Super P) and polyvinylidene fluoride (PVDF), and further ground after adding NMP to prepare a blue niobium oxide negative electrode material.

[0013] In the step (1), Nb2O5 and NbO2 are Nb 5+ With Nb 4+ Weigh the materials in a molar ratio of 5:1 to 1:1.

[0014] In the step (1), the mixture is thoroughly mixed on a mixer for 10 to 30 minutes and ground for 0.5 to 1 hour.

[0015] The precursor flakes in step (1) have a diameter of 10 mm, a thickness of 0.2 to 0.4 mm, and weigh 0.2 to 0.5 g per flake.

[0016] The calcination conditions in step (2) are to increase the temperature to 1100-1400° C. at a rate of 5° C. / min and keep the temperature for 5 hours. The calcination atmosphere is argon.

[0017] The cooling condition of step (2) is to reduce the temperature from 1200°C to 300°C to 600°C at a rate of 5°C / min, then cool to room temperature in the furnace, then cool to room temperature in the furnace, and grind for 10 to 20 minutes.

[0018] The drying condition of step (3) is vacuum drying at 80° C. for 12 h.

[0019] In the step (3), the active material is mixed with conductive carbon black (Super P) and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1, and the mass ratio of N-methylpyrrolidone (NMP) to the active material is 6:1, 5:1, and 4:1, and further ground for 10-30 minutes.

[0020] The blue niobium oxide negative electrode material is coated on the electrode and used for fast-charging lithium-ion batteries.

[0021] Advantages of the present invention:

[0022] (1) Due to its inherent Wadsley-Roth shear structure, the blue niobium oxide negative electrode material prepared in the present invention has extremely high electronic conductivity.

[0023] (1) Compared with T-Nb2O5 and H-Nb2O5 negative electrode materials, the blue niobium oxide negative electrode material prepared in the present invention has continuous redox reactions below 2V and has multiple discharge platforms (1.1 - 2.1V). Therefore, it has a higher capacity, stable discharge, and a slow voltage drop rate. The discharge specific capacities at 0.25C, 0.5C, 1C, 2.5C, 5C, 10C, and 25C are 262.55 mAh g -1 , 238.76 mAh g -1 , 223.80 mAh g -1 , 206.10 mAh g -1 , 187.72 mAh g -1 , 168.67 mAh g -1 , 142.64 mAh g -1 .

[0024] (4) The initial Coulombic efficiency of the blue niobium oxide negative electrode material prepared in the present invention is 100%, and after cycling at different current densities and returning to the initial current density, its capacity retention rate is still as high as 94.96%.

[0025] (5) The blue niobium oxide negative electrode material prepared in the present invention is a micron-sized powder with a particle size of 3 - 5 μm. Compared with nanomaterials, it has a higher volume energy density, is not prone to agglomeration and capacity reduction, and has a volume expansion rate smaller than that of nanomaterials, so its structure is more stable;

[0026] (5) The gas-phase solid sintering treatment technology invented in the present invention has a simple process, high sample yield, small material loss, and low cost, and has more commercial value compared with other preparation methods. Description of the Drawings

[0027] Figure 1 is the X-ray diffraction pattern of the niobium oxide negative electrode material prepared in the present invention.

[0028] Figure 2 is the ordinary photo of the niobium oxide negative electrode material prepared in the present invention and the scanning electron micrograph taken after magnifying 8000 times.

[0029] Figure 3It is the cyclic performance graph and dQ / dV curve of the niobium oxide negative electrode material prepared by the present invention in the first three cycles at 0.25C.

[0030] Figure 4 It is the cyclic performance graph and dQ / dV curve of the niobium oxide negative electrode material prepared by the present invention at 0.25C, 0.5C, 1C, 2.5C, 5C, 10C, and 25C.

[0031] Figure 5 It is the rate performance graph of the niobium oxide negative electrode material prepared by the present invention at 0.25C, 0.5C, 1C, 2.5C, 5C, 10C, and 25C and the comparison graph of this work with similar materials. Detailed implementation manners

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0033] Example 1:

[0034] 1) Weigh Nb2O5 and NbO2 according to the molar ratio of Nb 5+ and Nb 4+ of 5:1, mix them thoroughly (20 min) and grind them (0.5 h) on a mixer, and press tablets (0.2 g); obtain precursor thin slices (with a thickness of 0.2 mm);

[0035] (2) Place the precursor thin slices described in step (1) in a tubular furnace with Ar flowing through it for calcination. Heat it to 1200°C at a rate of 5°C / min, keep it warm for 5 h, then cool it to 500°C at a rate of 5°C / min and then cool it to room temperature with the furnace and grind it (20 min) to obtain blue niobium oxide powder.

[0036] Example 2:

[0037] 1) Weigh Nb2O5 and NbO2 according to the molar ratio of Nb 5+ and Nb 4+ of 2.5:1, mix them thoroughly (20 min) and grind them (0.5 h) on a mixer, and press tablets (0.2 g); obtain precursor thin slices (with a thickness of 0.2 mm);

[0038] (2) Place the precursor thin slices described in step (1) in a tubular furnace with Ar flowing through it for calcination. Heat it to 1200°C at a rate of 5°C / min, keep it warm for 5 h, then cool it to 500°C at a rate of 5°C / min and then cool it to room temperature with the furnace and grind it (20 min) to obtain blue niobium oxide powder;

[0039] Example 3:

[0040] 1) Weigh Nb2O5 and NbO2 according to the molar ratio of Nb 5+ and Nb 4+Weigh the materials in a molar ratio of 2.5:1, mix them thoroughly (for 20 min) and grind them (for 1 h) on a mixer, and then press them into tablets (0.5 g); obtain precursor thin slices (with a thickness of 0.4 mm);

[0041] (2) Place the precursor thin slices described in step (1) in a tubular furnace with Ar flowing through and calcine them. Heat them to 1200 °C at a rate of 5 °C / min, keep the temperature for 5 h, then cool them to 500 °C at a rate of 5 °C / min and then cool them to room temperature with the furnace and grind them (for 20 min) to obtain blue niobium oxide powder;

[0042] As Figure 1 shown: The obtained material is a pure phase.

[0043] As Figure 2 shown: The obtained material presents a short rod shape, and the particle size is about 3 - 5 μm.

[0044] As Figure 3 shown: At 0.25 C, in the voltage range of 1.1 V - 2.1 V, the charge-discharge curve shows multiple charge-discharge platforms, corresponding to multiple redox peaks.

[0045] As Figure 4 shown: From 0.25 C to 25 C, the capacity of the battery decreases slowly, and it can maintain a specific capacity of 142.64 mAh g -1 at 25 C.

[0046] As Figure 5 shown: Compared with other materials of the same type, its rate performance is more prominent.

[0047] The blue niobium oxide negative electrode material powder prepared by the present invention is granular, and the primary particle size is about 3 - 5 μm. It can be directly assembled into a fast-charging lithium-ion battery without undergoing secondary treatment. Due to the fast Li + diffusion rate, good electronic conductivity and structural stability, the blue niobium oxide negative electrode material exhibits excellent lithium-ion storage specific capacity (262.55 mAh g -1 at 0.25 C), charge-discharge rate (142.64 mAh g -1 at 25 C) and a Coulomb efficiency close to 100%, meeting the fast-charging requirements of power batteries.

[0048] The present invention provides an idea and method, which is not limited to the specific embodiments listed above. Those skilled in the art can make various equivalent modifications and equivalent substitutions according to the working principle of the present invention and the specific embodiments given above, so as to form more new embodiments. These improvements should also be regarded as within the protection scope of the present invention.

Claims

1. A preparation method of a blue niobium oxide negative electrode material, characterized in that, The steps include: Step (1): weigh Nb2O5 and NbO2, fully mix and grind them on a mixer, and press them into sheets to obtain precursor sheets; Step (2): placing the precursor flakes described in step (1) in a tubular furnace filled with Ar for calcination and heat preservation, cooling to room temperature, and grinding to obtain blue niobium oxide powder; Step (3): crushing the blue niobium oxide powder obtained in step (2) with a mortar, grinding, and drying, using it as an active material, mixing it with conductive carbon black and polyvinylidene fluoride, adding NMP, and further grinding it to prepare a blue niobium oxide negative electrode material; The blue niobium oxide negative electrode material has a primary particle size of 3 to 5 μm, micron-sized particles, short rod-shaped, and has strong adhesion; In the step (1), Nb2O5 and NbO2 are Nb 5+ With Nb 4+ Weigh the material at a molar ratio of 5:1 to 1:1; The calcination conditions in step (2) are heated at a rate of 5 o °C / min to 1100 - 1400 °C, held for 5 h, and the atmosphere used for calcination is argon.

2. The preparation method of a blue niobium oxide negative electrode material according to claim 1, characterized in that, In the step (1), the mixture is thoroughly mixed on a mixer for 10 to 30 minutes and ground for 0.5 to 1 hour.

3. The preparation method of a blue niobium oxide negative electrode material according to claim 1, wherein, The precursor flakes in step (1) have a diameter of 10 mm, a thickness of 0.2 to 0.4 mm, and each flake weighs 0.2 to 0.5 g.

4. The preparation method of a blue niobium oxide negative electrode material according to claim 1, characterized in that, The cooling condition of step (2) is to reduce the temperature from 1200°C to 300°C to 600°C at 5°C / min, then cool to room temperature in the furnace, then cool to room temperature in the furnace, and grind for 10 to 20 minutes.

5. The preparation method of a blue niobium oxide negative electrode material according to claim 1, characterized in that, The drying conditions of step (3) are vacuum drying at 80°C for 12 h.

6. The preparation method of a blue niobium oxide negative electrode material according to claim 1, characterized in that, In the step (3), the active material is mixed with conductive carbon black and polyvinylidene fluoride in a mass ratio of 8:1:1, and the mass ratio of N-methylpyrrolidone to the active material is 6:1, 5:1 or 4:1, and further ground for 10 to 30 minutes.

7. A method for preparing a blue niobium oxide negative electrode material according to any one of claims 1-6, characterized in that, The blue niobium oxide negative electrode material is coated on an electrode and is used for fast-charging lithium-ion batteries.

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