CN104201363B - The coated Li of a kind of carbon3VO4Lithium ion battery cathode material and its preparation method - Google Patents

Abstract

The invention provides a carbon _- coated _Li3VO4 negative electrode material for a lithium ion battery. The negative electrode material uses vanadium pentoxide, lithium carbonate and hexamethylenetetramine as raw materials to obtain a mesophase solution through hydrothermal reaction, and then Add citric acid to the mesophase solution and mix evenly, dry to obtain a solid product, and sinter the solid product in a high-temperature atmosphere to obtain a negative electrode material for a lithium ion battery with amorphous carbon coated on the surface of Li ₃ VO ₄ , the negative electrode material It is granular, with a particle size of 90-120nm. The present invention utilizes the carbonization effect of citric acid to refine Li ₃ VO ₄ particles and uniformly coat the carbon layer on the surface of the particles. The synthesis process is simple, easy to operate, and the material preparation cost is low. Li ₃ VO ₄ in the prepared samples is uniform nanoparticles with a size of 90-120nm. In the obtained sample, the amorphous carbon is uniformly coated on the surface of Li ₃ VO ₄ particles. The prepared material has high charge-discharge capacity and excellent cycle performance.

Description

A kind of carbon-coated Li3VO4 lithium-ion battery negative electrode material and preparation method thereof

technical field

The invention relates to a new type of lithium-ion battery composite negative electrode material, in particular to a preparation technology of a carbon _- coated _Li3VO4 composite material and its lithium storage characteristics, belonging to the field of new electrochemical materials.

Background technique

Lithium-ion batteries have the advantages of high working voltage, large specific energy, stable discharge potential curve, small self-discharge, long cycle life, good low-temperature performance, no memory, and no pollution. They have been widely used in mobile communication devices such as notebook computers and mobile phones Among them, it also has broad application prospects in future electric vehicles such as electric vehicles and electric bicycles. A key factor affecting the development of lithium-ion batteries lies in the development and application of positive and negative electrode materials. As a new type _{of anode} material, Li _{3 VO 4} has higher volume specific capacity and better safety performance than commercial graphite anode materials, and has higher The specific capacity, lower charge and discharge voltage, and the current commercial cathode materials are well matched, and have broad application prospects in lithium-ion batteries. Studies have shown that combining Li ₃ VO ₄ and graphene can significantly improve its capacity and cycle stability, but the cost of graphene is too high to be conducive to large-scale preparation. In addition, direct deposition of Li ₃ VO ₄ on nickel foam also effectively improved its electrochemical performance. The preparation of carbon-coated Li ₃ VO ₄ composite structure by a simple method is expected to improve the electrochemical performance of Li ₃ VO ₄ materials, and it is also of great significance for the practical application of Li ₃ VO ₄ in lithium-ion batteries. So far, the preparation of carbon _- coated _Li3VO4 composite structure and its application in lithium-ion batteries have not been reported. Based on the above background, this patent invented an effective method to prepare carbon-coated Li ₃ VO ₄ nanoparticle composite structure, and the prepared carbon-coated Li ₃ VO ₄ composite material showed high specific capacity and Excellent cycle stability.

Contents of the invention

The purpose of the present invention is to use vanadium pentoxide, lithium carbonate, hexamethylenetetramine and citric acid as precursors to prepare a new carbon-coated _Li3VO4 lithium _- ion battery composite material through hydrothermal reaction combined with high-temperature sintering . The principle is to first prepare the precursor solution by hydrothermal reaction, then introduce citric acid and fully stir to mix the citric acid and the precursor liquid evenly, dry and use high-temperature heating to provide reaction energy, and obtain carbon-coated _Li3 through solid-state reaction. VO ₄ nanoparticle composite structure.

_The raw materials for _Li3VO4 synthesis involved in the present invention are vanadium pentoxide, lithium carbonate, hexamethylenetetramine and citric acid. In the process of material preparation, vanadium pentoxide, lithium carbonate and hexamethylenetetramine are weighed according to the feeding molar ratio of 1:3:5, placed in a beaker and mixed with an appropriate amount of distilled water, and then placed in a hydrothermal reaction React in the kettle at 120~180°C for 12~48 hours. Transfer the solution obtained from the reaction to a beaker and add a certain amount of citric acid. After fully stirring, dry it in an oven. Finally, heat it to 500-600°C under nitrogen and sinter it for 2-10 hours. Cool naturally to obtain a carbon package. Cover Li ₃ VO ₄ samples.

The carbon-coated Li ₃ VO ₄ negative electrode material and preparation method involved in the present invention have the following salient features:

(1) The present invention utilizes the carbonization of citric acid to refine the Li ₃ VO ₄ particles and uniformly coat the carbon layer on the surface of the particles.

(2) The synthesis process is simple, easy to operate, and the material preparation cost is low.

(3) Li ₃ VO ₄ in the prepared samples is uniform nanoparticles with a size of 90~120nm.

(4) The amorphous carbon in the obtained sample is evenly coated on the surface of Li ₃ VO ₄ particles.

(5) The prepared material has high charge-discharge capacity and excellent cycle performance.

Description of drawings

The XRD spectrum of the sample prepared in Fig. 1 Example 1.

The Raman spectrum of the sample prepared in Fig. 2 Example 1.

The SEM picture (a) and the TEM picture (b) of the sample prepared in Fig. 3 Example 1.

Fig. 4 is the first charge and discharge curve (a) and cycle performance graph (b) of the sample prepared in Example 1 (current density 0.1mAcm ^-2 ).

Fig. 5 is the first charge and discharge curve (a) and cycle performance graph (b) of the sample prepared in Example 2 (current density 0.1mAcm ^-2 ).

Fig. 6 is the first charge and discharge curve (a) and cycle performance graph (b) of the sample prepared in Example 3 (current density 0.1mAcm ^-2 ).

detailed description

Example 1

Weigh 1mmol of vanadium pentoxide, 3mmol of lithium carbonate and 5mmol of hexamethylenetetramine into a beaker, add an appropriate amount of distilled water and stir evenly, transfer to a hydrothermal ax to react at 140°C for 24 hours, transfer the resulting solution to the beaker and Add 0.05mmol citric acid, stir well and dry. The dried product was placed in a crucible, and the crucible was moved into a high-temperature tube furnace, calcined at 550°C under nitrogen for 5 hours, and cooled naturally to obtain a carbon-coated Li ₃ VO ₄ sample. The results showed that the as-prepared samples were analyzed by XRD patterns, and the ions located at 16.3 ^o , 21.6 ^o , 22.9 ^o , 24.4 ^o , 28.2 ^o , 32.8 ^o , 36.3 ^o , 37.6 ^o , 49.8 ^o , 58.7 ^o , 66.2 ^o and 70.9 ^o _The diffraction peaks correspond to ₍ 100), (110), (011), (101), (111), (200), ( 002), (201), (202), (320), (203) and (322) crystal planes. The prepared samples were analyzed by Raman, and the peaks located at 1358 and 1601 cm ^-1 were derived from carbon. The prepared carbon-coated Li ₃ VO ₄ composite was characterized by SEM and TEM. It can be seen from Figure 3(a) that Li ₃ VO ₄ is a nanoparticle with an average size of about 100nm. It can be seen from Figure 3(b) that carbon is uniformly coated on the surface of Li ₃ VO ₄ nanoparticles. Using the prepared carbon-coated Li ₃ VO ₄ nanoparticles as the negative electrode material of lithium-ion batteries shows that the first charge and discharge capacities are 537 and 688mAh/g, and after 100 cycles, the charge and discharge capacities are both 562 and 565mAh/g, showing High specific capacity and excellent cycle stability.

Example 2

Weigh 1mmol of vanadium pentoxide, 3mmol of lithium carbonate and 5mmol of hexamethylenetetramine into a beaker, add an appropriate amount of distilled water and stir evenly, transfer to a hydrothermal ax to react at 140°C for 24 hours, transfer the resulting solution to the beaker and Add 0.05mmol citric acid, stir well and dry. The dried product was placed in a crucible, and the crucible was moved into a high-temperature tube furnace, calcined at 500°C under nitrogen for 5 hours, and cooled naturally to obtain a carbon-coated Li ₃ VO ₄ sample. The results show that the prepared carbon-coated Li ₃ VO ₄ nanoparticles are used as the negative electrode material of lithium-ion batteries to show the first charge and discharge capacities of 355 and 445mAh/g, and the charge and discharge capacities of 419 and 420mAh/g after 100 cycles. , showing high specific capacity and good cycle stability.

Example 3

Weigh and weigh 1mmol of vanadium pentoxide, 3mmol of lithium carbonate and 5mmol of hexamethylenetetramine into a beaker, add an appropriate amount of distilled water and stir evenly, transfer to a hydrothermal ax to react at 140°C for 24 hours, and transfer the resulting solution to the beaker And add 0.05mmol citric acid, fully stir and dry. The dried product was placed in a crucible, and the crucible was moved into a high-temperature tube furnace, calcined at 600°C under nitrogen for 5 hours, and cooled naturally to obtain a carbon-coated Li ₃ VO ₄ sample. The results show that the prepared carbon-coated Li ₃ VO ₄ nanoparticles are used as the negative electrode material of lithium-ion batteries, showing the first charge and discharge capacities of 494 and 620mAh/g, and the charge and discharge capacities of 496 and 498mAh/g after 100 cycles. , showing high specific capacity and excellent cycling stability.

Claims (1)

1. _A carbon-coated _Li3VO4 negative electrode material for lithium ion batteries, characterized in that: the negative electrode material is made of vanadium pentoxide, lithium carbonate, hexamethylenetetramine and citric acid as basic raw materials Carbon-coated Li ₃ VO ₄ lithium ion battery negative electrode material, the particle size of the negative electrode material is 90-120nm, and the XRD spectrum is located at 16.3 ^o , 21.6 ^o , 22.9 ^o , 24.4 ^o , 28.2 ^o , 32.8 ^o , 36.3 ^o , 37.6 _The diffraction peaks at ^o , 49.8 ^o , 58.7 ^o , 66.2 ^o and 70.9 ^o correspond to ₍ 100), (110), (011), (011) and (101), (111), (200), (002), (201), (202), (320), (203) and (322) crystal faces; The specific preparation method is to use 1mmol of vanadium pentoxide, 3mmol of lithium carbonate and 5mmol of hexamethylenetetramine as raw materials to obtain a mesophase solution through hydrothermal reaction, and then add 0.05mmol of citric acid to the mesophase solution and mix evenly. drying to obtain a solid product, and sintering the solid product in a high-temperature atmosphere to obtain a carbon-coated Li ₃ VO ₄ lithium-ion battery negative electrode material; the hydrothermal reaction temperature is 120-180°C, and the reaction time is 12-48 hours; the high-temperature atmosphere is nitrogen, the sintering temperature is 500-600° C., and the sintering time is 2-10 hours, the carbon-coated Li ₃ VO ₄ lithium-ion battery negative electrode material can be prepared.