A battery negative electrode sheet and its preparation method and application

Abstract

The present invention discloses a battery negative electrode plate and its preparation method and application. The negative electrode plate is a layered structure, including an intermediate layer and a titanium nitride nanofiber coating layer. The intermediate layer is a carbon nanotube aerogel film composed of a carbon nanotube skeleton. The titanium nitride nanofiber coating layer is provided on the surface of the carbon nanotube aerogel film. The intermediate layer has a three-dimensional porous structure, is sponge-like and elastic, and can rebound to its original shape after compression. The preparation method is to first prepare a carbon nanotube aerogel film, and then use an electrostatic spinning spray method to coat titanium-containing precursor fibers on the surface of the carbon nanotube aerogel film, and then heat treat it in a nitrogen atmosphere to form a titanium nitride nanofiber coating layer. The battery negative electrode plate prepared by the present invention can be used for lithium ion batteries, sodium ion batteries or potassium ion batteries, and has high efficiency in transporting and storing active alkali metal ions, stable structure and good electrochemical performance; the preparation process of the present invention is simple and has broad commercial application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery material processing, and in particular relates to a battery negative electrode sheet and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries are the absolute mainstream of today's battery industry. They are developing rapidly and have promoted revolutionary progress in many fields such as smartphones, laptops and electric vehicles. However, lithium is a relatively scarce element, so people have been looking for a new rechargeable battery to replace lithium batteries. The reserves of sodium and potassium in the earth's crust are thousands of times that of lithium, and their properties are similar to lithium. Sodium-ion batteries and potassium-ion batteries have a similar "rocking chair" charging and discharging principle as lithium-ion batteries, so they are highly expected.

[0003] However, graphite, a common negative electrode in lithium-ion batteries, is not suitable for sodium / potassium ion batteries because the larger diameter of sodium / potassium ions cannot be intercalated and deintercalated between graphite layers. In addition, sodium / potassium ions cannot form a stable phase structure with graphite. Other negative electrode materials for sodium / potassium ion batteries were also studied at the same time, including graphitized hard carbon, alloys, oxides, and organic composites. However, most of the current negative electrode materials will produce a large volume expansion during the sodium / potassium ion embedding process, resulting in irreversible capacity decay.

[0004] In order to solve the above problems in the prior art, the present invention is provided. Summary of the invention

[0005] In view of at least one of the above-mentioned technical problems, the object of the present invention is to provide a battery negative electrode plate and a preparation method and application thereof. The preparation method uses freeze-drying technology to prepare a three-dimensional porous carbon nanotube aerogel material, and then electrostatically sprays titanium-containing fibers on its surface, and heat-treats it again in a nitrogen atmosphere to convert it into titanium nitride nanofibers, which are then coated on the upper and lower surfaces of the carbon nanotube aerogel to obtain a three-dimensional negative electrode plate with stable structure, high elasticity, good conductivity, and high efficiency in transporting and storing metals.

[0006] The technical solution of the present invention is:

[0007] The invention relates to a battery negative electrode plate, which is a layered structure, including an intermediate layer and a titanium nitride nanofiber coating layer. The intermediate layer is a carbon nanotube aerogel film composed of a carbon nanotube skeleton, and the titanium nitride nanofiber coating layer is provided on the surface of the carbon nanotube aerogel film. The intermediate layer has a three-dimensional porous structure, is sponge-like and elastic, and can rebound to its original shape after being compressed.

[0008] Preferably, it also includes a current collector substrate, the intermediate layer is provided on the upper and lower surfaces of the current collector substrate, and the titanium nitride nanofiber coating layer is provided on the upper surface of the intermediate layer located on the upper side of the current collector substrate and the lower surface of the intermediate layer located on the lower side of the current collector substrate.

[0009] The present invention also relates to a method for preparing a negative electrode sheet of a battery, comprising the following steps:

[0010] Step 1, preparing a carbon nanotube aerogel film: first preparing a carbon nanotube slurry, then coating it on the surface of a current collector substrate, and freeze-drying it;

[0011] Step 2: coating titanium nitride nanofibers: coating titanium-containing precursor fibers on the surface of the carbon nanotube aerogel membrane by an electrospinning spray method, and then heat treating it in a nitrogen atmosphere to obtain a negative electrode of the battery, and a titanium nitride nanofiber coating layer is formed on the surface of the carbon nanotube aerogel membrane.

[0012] Preferably, in step 1, the prepared carbon nanotube slurry is made of a solvent, carbon nanotubes, a binder and a stabilizer, and the specific preparation process is: disperse the carbon nanotubes in a solvent, add a certain amount of binder and stabilizer, and stir continuously at a speed of 200 to 300 revolutions per minute for 20 to 30 minutes to fully mix and obtain the carbon nanotube slurry. The concentration of the carbon nanotube slurry is 10% to 15%, and the mass ratio of carbon nanotubes to binder and stabilizer is 20 to 10:0.7:0.3.

[0013] Preferably, in step 1, after the carbon nanotube slurry is coated on the surface of the current collector substrate, it is transferred into a liquid ammonia freeze dehydration tank and then into a low-temperature drying chamber to obtain a carbon nanotube aerogel film.

[0014] Preferably, the solvent is at least one of deionized water, alcohol, ethylene glycol, propanol, isopropanol, acetone, and N-methylpyrrolidone;

[0015] The binder is at least one of polyvinyl pyrrolidone, polyvinyl alcohol, polytetrafluoroethylene, polyethylene terephthalate, polybutylene terephthalate, perfluorosulfonic acid polymer (nafion), alginate (lithium, sodium or potassium salt), and pectinate (lithium, sodium or potassium salt);

[0016] The stabilizer is sodium carboxymethyl cellulose (CMC).

[0017] Preferably, in step 1, the carbon nanotube is at least one of a single-walled carbon nanotube and a multi-walled carbon nanotube; the purity of the carbon nanotube is greater than 99%, the diameter is 10 to 200 nm, and the length is 5 to 20 μm;

[0018] The current collector substrate is one of copper foil, aluminum foil, copper mesh and aluminum mesh.

[0019] Preferably, in step 2, the electrospinning method comprises the following steps:

[0020] 1) Preparation of electrospinning solution: titanate is added to a solution of N,N-dimethylformamide and anhydrous ethanol in a volume ratio of 2:1, and then polyvinyl pyrrolidone is added and stirred evenly to prepare an electrospinning solution;

[0021] 2) Electrospinning spraying: injecting the electrospinning solution into a syringe with a spinneret for spinning;

[0022] 3) Heat treatment: placing the double-sided coated carbon nanotube aerogel film in a tubular furnace, heat treating it at 1000° C. to 1400° C. for 2 to 5 hours in a nitrogen atmosphere, and cooling it to room temperature in the furnace to obtain the battery negative electrode sheet.

[0023] Preferably, in step 1), the concentration of titanate in the electrospinning solution is 0.05 mol / L to 0.1 mol / L, and the concentration of polyvinyl pyrrolidone is 0.5 mmol / L to 0.8 mmol / L;

[0024] The titanate is at least one of n-butyl titanate, n-propyl titanate, isopropyl titanate, and ethyl titanate.

[0025] Preferably, in step 2), the spinning voltage is set to 10 kV to 30 kV, the propulsion speed is 0.001 mm / s, the fiber is double-sided sprayed on the surface of the carbon nanotube aerogel film, and the receiving distance is 5 cm to 15 cm.

[0026] The present invention also relates to the application of the above-mentioned battery negative electrode plate in the manufacture of lithium / sodium / potassium ion batteries. The battery negative electrode plate is a layered structure, wherein the interlayer is an aerogel composed of a carbon nanotube skeleton, and the surface of the aerogel is coated with a titanium nitride nanofiber coating layer. The carbon nanotube aerogel main material carbon nanotube is a good ion conductor and electron conductor, which can well guide the metal lithium (sodium or potassium) to be uniformly electroplated along the direction of the carbon tube, avoiding the random nucleation and growth of the metal on the negative electrode surface; the carbon nanotube aerogel film is three-dimensionally porous and has a large pore volume, which is conducive to the storage of metal lithium (sodium or potassium); titanium nitride nanofibers have good electrical conductivity, and coating on the surface of the aerogel film can effectively reduce the penetration of the electrolyte, thereby reducing the direct contact between the active alkali metal (lithium, sodium or potassium) and the electrolyte, and ensuring the chemical stability of the active alkali metal. The battery negative electrode plate can be used for the negative electrode of lithium, sodium or potassium ion batteries, with good electrochemical performance, high metal storage efficiency and stable structure.

[0027] The beneficial effects of the present invention are:

[0028] 1) The preparation method of the present invention is simple, the product consistency is good, the operability is strong, and it has a wide range of commercial application prospects;

[0029] 2) The three-dimensional porous structure inside the pole piece is extremely elastic, which can control the volume change of the negative electrode within 10%, greatly alleviating the huge volume expansion during the charge and discharge process; the large pore volume inside the aerogel is conducive to the storage of lithium, sodium or potassium ions; carbon nanotubes are good ion conductors and electron conductors, which can well guide the uniform electroplating of metallic lithium (sodium or potassium) along the direction of the carbon tube, avoiding random nucleation and growth of metal on the negative electrode surface, thereby inhibiting the generation of lithium (sodium or potassium) dendrites;

[0030] 3) The titanium nitride nanofibers on the outside of the pole piece have good conductivity. Coating them on the surface of the aerogel film can effectively reduce the penetration of the electrolyte, thereby reducing the direct contact between the active alkali metal (lithium, sodium or potassium) and the electrolyte, ensuring the chemical stability of the active alkali metal, and effectively improving the initial efficiency and cycle performance of the battery;

[0031] 4) The battery negative electrode sheet prepared by the present invention has good conductivity and high efficiency in storing and transporting metals, and is suitable for lithium (sodium or potassium) ion batteries. When the battery negative electrode sheet is applied to a battery, the prepared battery has the advantages of high capacity, high initial efficiency, good rate performance and good cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0033] Figure 1 This is a schematic diagram of the structure of the negative electrode sheet of a battery manufactured according to an embodiment of the present invention;

[0034] Figure 2 This is a SEM photograph of titanium nitride nanofibers on the surface of the negative electrode plate of the battery prepared in Example 1 of the present invention.

[0035] In the figure: 1-1 is a titanium nitride nanofiber layer; 1-2 is a current collector substrate; 1-3 is a carbon nanotube aerogel film. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0037] Example 1

[0038] 10 kg of carbon nanotubes (Suzhou First Element, CNTp, the same below) were added to 90 kg of 40% alcohol solution, and after ultrasonic treatment, 7 kg of 10% sodium pectate solution and 3 kg of 10% sodium carboxymethyl cellulose solution were added to the mixture, and the mixture was stirred at a rate of 200 revolutions per minute for 30 minutes to make it fully mixed, so as to obtain carbon nanotube slurry; the carbon nanotube slurry was coated on the surface of aluminum foil, and sent to a liquid ammonia freeze dehydration tank through a conveyor, and then into a -10°C low-temperature drying chamber to obtain a carbon nanotube aerogel film;

[0039] 10g of n-butyl titanate was added to 75mL of a solution of N,N-dimethylformamide and anhydrous ethanol in a volume ratio of 2:1, and then 5g of polyvinyl pyrrolidone was added, and the mixture was stirred for 12h to be uniformly mixed to obtain an electrospinning solution; the electrospinning solution was injected into a syringe with a spinneret for spinning, the spinning voltage was set to 20kV, the propulsion speed was 0.001mm / s, and the fiber was sprayed on both sides of the carbon nanotube aerogel film surface at a receiving distance of 10cm; the double-sided coated carbon nanotube aerogel film was placed in a tubular furnace, heat treated at 1250°C for 3h under a nitrogen atmosphere, and cooled to room temperature with the furnace to obtain the battery negative electrode sheet, such as Figure 1 As shown, the carbon nanotube aerogel film serves as an intermediate layer, and the negative electrode plate of the battery is a layered structure, which is composed of a titanium nitride nanofiber layer, a carbon nanotube aerogel film, a current collector substrate, a carbon nanotube aerogel film and a titanium nitride nanofiber layer distributed in sequence from top to bottom.

[0040] The carbon nanotube aerogel sample obtained in this example has a thickness of 30 μm and an area density of 19.8 g / m 2 , porosity 70%, which is conducive to the transportation and storage of metallic sodium; the titanium nitride nanofiber coating layer on its surface is 20nm thick, and its SEM image is as follows Figure 2 As shown, the fiber diameter is about 5 nm.

[0041] The electrochemical performance of the negative electrode of the battery prepared in this example was evaluated using sodium metal foil as the counter electrode and CR2032 button cell as the simulated battery. 1M NaClO4 (EC / DEC = 1:1 volume ratio) was used as the electrolyte and glass fiber as the diaphragm. The battery was assembled in an argon-filled glove box. Constant current charge and discharge tests were performed on a LAND CT2001 battery tester with a charge and discharge range of 0.01V to 3.0V. The battery's initial efficiency was 92.1% at 100mA·g -1 After 200 cycles at the same current density, the capacity can still be maintained at 1128.4 mAh g -1 , the material can also have excellent capacity retention during the cycle process.

[0042] Example 2

[0043] 10 kg of carbon nanotubes are added to 90 kg of 50% alcohol solution, and after ultrasonic treatment, 7 kg of 10% polyvinyl alcohol solution and 3 kg of 10% sodium carboxymethyl cellulose solution are added to the mixture, and the mixture is stirred at a rate of 200 revolutions per minute for 30 minutes to be fully mixed to obtain the carbon nanotube slurry; the carbon nanotube slurry is coated on the surface of an aluminum mesh, and sent to a liquid ammonia freeze dehydration tank through a conveyor, and then to a -10°C low-temperature drying chamber to obtain a carbon nanotube aerogel film;

[0044] 9.5 g of isopropyl titanate was added to 75 mL of a solution of N,N-dimethylformamide and anhydrous ethanol in a volume ratio of 2:1, and then 5 g of polyvinyl pyrrolidone was added, and the mixture was stirred for 12 h to be evenly mixed to obtain an electrospinning solution; the electrospinning solution was injected into a syringe with a spinneret for spinning, the spinning voltage was set to 15 kV, the propulsion speed was set to 0.001 mm / s, and the fiber was sprayed on both sides of the carbon nanotube aerogel film surface at a receiving distance of 5 cm; the double-sided coated carbon nanotube aerogel film was placed in a tubular furnace, heat treated at 1150° C. for 3.5 h in a nitrogen atmosphere, and cooled to room temperature with the furnace to obtain the battery negative electrode sheet.

[0045] The thickness of the negative electrode sheet of the battery obtained in this embodiment is 25 μm, and the surface density is 16.6 g / m 2 , porosity 68%, the titanium nitride nanofiber coating layer on its surface is 15nm thick, and the fiber diameter is about 5nm.

[0046] A CR2032 button battery was assembled in a glove box filled with argon using a potassium metal sheet as the counter electrode, 1M KClO4 (EC / DEC = 1:1 volume ratio) as the electrolyte, and glass fiber as the separator. Constant current charge and discharge performance tests were performed on the LAND battery test system with a charge and discharge range of 0.01V to 3.0V. The battery's initial efficiency was 91.6% at 20mA·g -1 After 200 cycles at the same current density, the capacity can still be maintained at 590.7 mAh g -1 , the material can also have excellent capacity retention during the cycle process.

[0047] Example 3

[0048] 10 kg of carbon nanotubes are added to 90 kg of 40% alcohol solution, and after ultrasonic treatment, 7 kg of 10% polyvinyl alcohol solution and 3 kg of 10% sodium carboxymethyl cellulose solution are added to the mixture, and the mixture is stirred at a rate of 200 revolutions per minute for 30 minutes to be fully mixed to obtain the carbon nanotube slurry; the carbon nanotube slurry is coated on the surface of copper foil, and sent to a liquid ammonia freeze dehydration tank through a conveyor, and then to a -10°C low-temperature drying chamber to obtain a carbon nanotube aerogel film;

[0049] 10g of n-butyl titanate is added to 75mL of a solution of N,N-dimethylformamide and anhydrous ethanol in a volume ratio of 2:1, and then 5g of polyvinyl pyrrolidone is added, and the mixture is stirred for 12h to be evenly mixed to obtain an electrospinning solution; the electrospinning solution is injected into a syringe with a spinneret for spinning, the spinning voltage is set to 20kV, the propulsion speed is set to 0.001mm / s, and the fiber is double-sidedly sprayed on the surface of the carbon nanotube aerogel film, and the receiving distance is 10cm; the double-sided coated carbon nanotube aerogel film is placed in a tubular furnace, heat treated at 1250°C for 3h in a nitrogen atmosphere, and cooled to room temperature with the furnace to obtain the battery negative electrode sheet.

[0050] The thickness of the negative electrode sheet of the battery obtained in this embodiment is 25 μm, and the surface density is 20 g / m 2 , porosity 60%, the titanium nitride nanofiber coating layer on its surface is 20nm thick, and the fiber diameter is about 5nm.

[0051] Using metallic lithium as the counter electrode, Cellgard 2400 as the separator, and 1M LiPF6 (EC / DMC=1:1 volume ratio) as the electrolyte, a CR2032 button battery was assembled in a glove box filled with argon. Constant current charge and discharge performance tests were performed on the LAND battery test system, with a charge and discharge range of 1.5V to 4.8V. The battery's initial efficiency was 93.2%, and at 20mA·g -1 After 500 cycles at the same current density, the capacity can still be maintained at 1963.6 mAh g -1 , the material can also have excellent capacity retention during the cycle process.

[0052] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

Claims

1. A battery negative electrode plate, characterized in that: The negative electrode plate of the battery is a layered structure, including an intermediate layer and a titanium nitride nanofiber coating layer, wherein the intermediate layer is a carbon nanotube aerogel film composed of a carbon nanotube skeleton, and the titanium nitride nanofiber coating layer is arranged on the surface of the carbon nanotube aerogel film, and the intermediate layer has a three-dimensional porous structure, is sponge-like and elastic, and can rebound to its original shape after compression; The preparation method of the carbon nanotube aerogel film is as follows: firstly, carbon nanotube slurry is prepared, then it is coated on the surface of a current collector substrate, and freeze-dried to obtain the film; wherein the prepared carbon nanotube slurry is made of a solvent, carbon nanotubes, a binder and a stabilizer, the concentration of the carbon nanotube slurry is 10% to 15%, and the mass ratio of carbon nanotubes to binder and stabilizer is 20 to 10:0.7:0.

3.

2. The negative electrode plate of the battery according to claim 1, characterized in that: It also includes a current collector substrate, the middle layer is provided on the upper and lower surfaces of the current collector substrate, and the titanium nitride nanofiber coating layer is provided on the upper surface of the middle layer located on the upper side of the current collector substrate and the lower surface of the middle layer located on the lower side of the current collector substrate.

3. A method for preparing a negative electrode sheet of a battery, characterized in that: The following steps are involved: Step 1, preparing a carbon nanotube aerogel film: first preparing a carbon nanotube slurry, then coating it on the surface of a current collector substrate, and freeze-drying it; wherein the prepared carbon nanotube slurry is made of a solvent, carbon nanotubes, a binder and a stabilizer, the concentration of the carbon nanotube slurry is 10% to 15%, and the mass ratio of carbon nanotubes to binder and stabilizer is 20 to 10:0.7:0.3; Step 2: coating titanium nitride nanofibers: coating titanium-containing precursor fibers on the surface of the carbon nanotube aerogel film by an electrospinning spray method, and then heat treating in a nitrogen atmosphere to obtain a negative electrode of the battery.

4. The preparation method according to claim 3, characterized in that: The solvent is at least one of deionized water, alcohol, ethylene glycol, propanol, isopropanol, acetone, and N-methylpyrrolidone; The binder is at least one of polyvinyl pyrrolidone, polyvinyl alcohol, polytetrafluoroethylene, polyethylene terephthalate, polybutylene terephthalate, perfluorosulfonic acid polymer, alginate (lithium, sodium or potassium salt), and pectinate (lithium, sodium or potassium salt); The stabilizer is sodium carboxymethyl cellulose.

5. The preparation method according to claim 3, characterized in that: In step 1, the carbon nanotube is at least one of a single-walled carbon nanotube and a multi-walled carbon nanotube; the purity of the carbon nanotube is greater than 99%, the diameter is 10 to 200 nm, and the length is 5 to 20 μm; The current collector substrate is one of copper foil, aluminum foil, copper mesh and aluminum mesh.

6. The preparation method according to claim 3, characterized in that: In step 2, the electrospinning method comprises the following steps: 1) Preparation of electrospinning solution: titanate is added to a solution of N,N-dimethylformamide and anhydrous ethanol in a volume ratio of 2:1, and then polyvinyl pyrrolidone is added and stirred evenly to prepare an electrospinning solution; 2) Electrospinning spraying: injecting the electrospinning solution into a syringe with a spinneret for spinning; 3) Heat treatment: placing the double-sided coated carbon nanotube aerogel film in a tubular furnace, heat treating it at 1000° C. to 1400° C. for 2 to 5 hours in a nitrogen atmosphere, and cooling it to room temperature in the furnace to obtain the battery negative electrode sheet.

7. The preparation method according to claim 6, characterized in that: In step 1), the concentration of titanate in the electrospinning solution is 0.05 mol / L to 0.1 mol / L, and the concentration of polyvinyl pyrrolidone is 0.5 mmol / L to 0.8 mmol / L; The titanate is at least one of n-butyl titanate, n-propyl titanate, isopropyl titanate, and ethyl titanate.

8. The preparation method according to claim 6, characterized in that: In step 2), the spinning voltage is set to 10 kV to 30 kV, the propulsion speed is 0.001 mm / s, the fiber is sprayed on both sides of the carbon nanotube aerogel film surface, and the receiving distance is 5 cm to 15 cm.

9. Use of the battery negative electrode sheet according to claim 1 in the manufacture of lithium / sodium / potassium ion batteries.

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