CN107978745B - High-capacity carbon nanotube composite cobalt sulfide negative electrode material and preparation and application thereof - Google Patents
High-capacity carbon nanotube composite cobalt sulfide negative electrode material and preparation and application thereof Download PDFInfo
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Abstract
The invention discloses a high-capacity carbon nanotube composite cobalt sulfide negative electrode material and a preparation method and application thereof, and belongs to the technical field of lithium ion batteries. The method utilizes the crystal water contained in the tetrahydrate cobalt acetate to perform hydrolysis reaction with the cobalt acetate to generate a rodlike cobalt-containing precursor, and under the action of PVP, the size of the cobalt-containing precursor is limited to obtain a rodlike precursor at a nanometer level, TAA reacts with the precursor to generate the rodlike cobalt sulfide, the crystallization performance of the material can be improved in the subsequent sintering process, the nanometer material uniformly compounded with the carbon nanotube is beneficial to reduction of internal resistance and transmission of electrons, and the electrochemical performance is greatly improved. The invention uses the freeze drying technology, and effectively avoids the problem that the carbon nano tube is easy to agglomerate. The obtained carbon nanotube composite CoS negative electrode material has high specific capacity, high charge-discharge capacity, high first coulombic efficiency and obviously improved capacity attenuation condition.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a high-capacity carbon nanotube composite cobalt sulfide cathode material, and a preparation method and application thereof.
Background
The lithium ion battery has the advantages of high working voltage, high specific capacity, good cycle performance, quick charging, no memory effect, environmental protection and the like, and is widely applied to many fields. The commercial lithium ion battery still adopts a carbon material as a negative electrode material, but the capacity of the material in the actual battery is low (the theoretical capacity is only 372mAh/g), and the material cannot meet the requirements of people. Therefore, the development of a negative electrode material with higher capacity is of great significance to the development of lithium ion batteries. Due to transition metal sulfides (MoS)2，FeS，NiS，CoS2Etc.) have very high specific capacity, and research on applying the same to lithium ion batteries is increasing. Wherein there are multiple stoichiometric ratios of cobalt sulfide (Co)1-xS，CoS，CoS2，Co3S4Etc.) have attracted interest to many researchers due to their unique electrochemical properties. In the research of a plurality of lithium ion battery cobalt sulfide cathode materials, due to the insertion and the removal of lithium ions, the volume of the electrode material can expand and even pulverize, so that the structure collapses, and irreversible elemental cobalt can be generated in the charging and discharging process, so that the reversible capacity and the cycling stability of the electrode material are reduced. Fortunately, the stress change in the charging and discharging process can be relieved by controlling the special shape and structure of the synthesis, the volume expansion is reduced, and the electrical conductivity and the cycling stability of the material can be improved by compounding with carbon nano tubes or graphene and the like, so that the electrochemical performance of the material is obviously improved.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention mainly aims to provide a preparation method of a high-capacity carbon nanotube composite cobalt sulfide negative electrode material for a lithium ion battery.
The invention also aims to provide the high-capacity carbon nano tube composite cobalt sulfide negative electrode material for the lithium ion battery, which is prepared by the preparation method.
The invention further aims to provide application of the high-capacity carbon nanotube composite cobalt sulfide negative electrode material for the lithium ion battery.
The purpose of the invention is realized by the following technical scheme:
a preparation method of a cobalt sulfide negative electrode material of a high-capacity lithium ion battery comprises the following steps:
(1) uniformly dissolving polyvinylpyrrolidone (PVP) in absolute ethyl alcohol under the stirring condition that the rotating speed is 400-700 rpm until the solution becomes clear;
(2) under the stirring condition of the rotation speed of 400-700 rpm, cobalt acetate tetrahydrate (Co (CH)3COO)2·4H2O) adding the cobalt-containing precursor into the solution obtained in the step (1), continuously stirring for 20-40 min at room temperature, standing for 40-50 h after cobalt acetate is uniformly dispersed, and obtaining a cobalt-containing precursor precipitate;
(3) centrifuging the solution of the precipitate generated in the step (2), removing supernatant, and washing with hot ethanol for 10-20 times to obtain a cobalt-containing precursor;
(4) drying the cobalt-containing precursor obtained in the step (3);
(5) under the condition of continuous stirring, adding a cobalt-containing precursor and Thioacetamide (TAA) into absolute ethyl alcohol according to a certain proportion, and continuously stirring for 30-40 min (preferably 35-40 min) under the condition that the stirring speed is 600-800 rpm to completely dissolve the cobalt-containing precursor and the thioacetamide;
(6) transferring the solution in the step (5) into a liner of a reaction kettle, putting the liner into a stainless steel reaction kettle, and keeping the temperature at 110-160 ℃ for 5-8 h to obtain cobalt sulfide (CoS);
(7) and calcining CoS at 400-600 ℃ for 4-6 h to improve the crystallinity of the CoS.
Preferably, the concentration of polyvinylpyrrolidone (PVP) in the solution in the step (1) is 15-25 g/L;
specifically, the absolute ethyl alcohol is 200mL, and when PVP is 3-5 g, the absolute ethyl alcohol can dissolve the PVP.
Preferably, the polyvinylpyrrolidone (PVP) K value in step (1) is 30, and PVP is a nonionic polymer compound.
Preferably, the mass ratio of the cobalt acetate tetrahydrate to the polyvinylpyrrolidone in the step (2) is (1-2): (3-5).
Preferably, the continuous stirring time in the step (2) at room temperature is 20-35 min;
preferably, the drying condition in the step (4) is drying for 2-6 h at the temperature of 60-80 ℃;
preferably, the mass ratio of the cobalt-containing precursor to Thioacetamide (TAA) in the step (5) is (7-9): (10-12.5).
A preparation method of a high-capacity carbon nanotube composite cobalt sulfide negative electrode material for a lithium ion battery comprises the following steps:
(A) adding carbon nanotubes into dilute nitric acid, performing ultrasonic treatment, continuously stirring at the rotation speed of 400-700 rpm, and heating the solution;
(B) carrying out suction filtration on the solution obtained in the step (A) to obtain a carbon nano tube, adding the carbon nano tube into concentrated nitric acid, continuously stirring at the rotating speed of 400-700 rpm, heating the solution, diluting the reacted solution, carrying out suction filtration and washing to obtain an oxidized carbon nano tube;
(C) freeze-drying the oxidized carbon nanotubes obtained in step (B);
(D) adding the CoS calcined in the step (7) into absolute ethyl alcohol under the condition of continuous stirring at the rotating speed of 600-800 rpm, adding the oxidized carbon nano tube into the solution, and continuously stirring for 40-60 min;
(E) and (D) carrying out suction filtration on the solution stirred in the step (D), and carrying out freeze drying to obtain the carbon nano tube composite cobalt sulfide negative electrode material.
Preferably, the heating condition in the step (A) is heating to 60-80 ℃ and keeping the temperature for 2-4 hours;
preferably, the concentration of the carbon nano tubes in the solution in the step (A) is 1-3 g/L;
preferably, the concentration of the dilute nitric acid in the step (A) is 1-3 mol/L;
preferably, the concentrated nitric acid in the step (B) is 65-68% of concentrated nitric acid;
preferably, the heating condition in the step (B) is heating to 60-80 ℃ and keeping the temperature for 4-6 hours;
preferably, the solution after the reaction in the step (B) is diluted by 8-12 times;
preferably, the freeze-drying time in the step (C) is 48-52 h;
preferably, the concentration of the cobalt sulfide in the solution in the step (D) is 1.6-2 g/L.
The mass ratio of the cobalt sulfide to the oxidized carbon nano tube is (16-20): (1-2).
A high-capacity carbon nanotube composite cobalt sulfide cathode material for a lithium ion battery is prepared by the preparation method.
The high-capacity carbon nanotube composite cobalt sulfide cathode material for the lithium ion battery is applied to the manufacturing of the lithium ion battery.
The principle of the invention is as follows: the crystal water contained in the cobalt acetate tetrahydrate and the cobalt acetate undergo hydrolysis reaction to generate a rod-shaped cobalt-containing precursor, and the size of the cobalt-containing precursor is limited under the action of PVP (polyvinyl pyrrolidone) to obtain a rod-shaped precursor at a nanometer level, the TAA reacts with the precursor to generate the cobalt sulfide at the nanometer rod shape, the crystallization performance of the material can be improved in the subsequent sintering process, the nanometer material uniformly compounded with the carbon nanotube is beneficial to reduction of internal resistance and transmission of electrons, and the electrochemical performance is greatly improved.
Compared with the prior art, the invention has the following advantages and effects:
(1) the invention introduces PVP, which can limit the size of the material well.
(2) The invention uses the freeze drying technology, and effectively avoids the problem that the carbon nano tube is easy to agglomerate.
(3) The carbon nanotube composite CoS negative electrode material prepared by the preparation method has high specific capacity, high charge and discharge capacity, high first coulombic efficiency and obviously improved capacity attenuation condition. In addition, the carbon nano tube improves the electronic conductivity of the material, and is beneficial to improving the reaction kinetics performance, so that the electrochemical performance of the material is improved.
Drawings
Fig. 1 is an SEM image of the cobalt-containing precursor prepared in example 1.
FIG. 2 is a TEM image of CoS prepared in example 1.
Fig. 3 is an SEM image of CoS of the composite carbon nanotube prepared in example 1.
Fig. 4 is a graph showing the relationship between the specific discharge capacity and the number of cycles of the lithium ion battery manufactured by the CoS negative electrode material of the composite carbon nanotube prepared in example 1 and the CoS negative electrode material prepared in the comparative example.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited thereto.
Example 1
A preparation method of a high-capacity carbon nanotube composite CoS negative electrode material for a lithium ion battery comprises the following steps:
firstly, preparing cobalt sulfide:
(1) under stirring at 500rpm, 3g of polyvinylpyrrolidone (PVP) was dissolved uniformly in 200mL of absolute ethanol until the solution became clear.
(2) Under stirring at 600rpm, 1.28g of cobalt acetate tetrahydrate (Co (CH)3COO)2·4H2O) is added into the solution, the mixture is continuously stirred for 20min at room temperature, and is kept stand for 48h after cobalt acetate is uniformly dispersed, so as to obtain a cobalt-containing precursor precipitate.
(3) And (3) centrifuging the solution of the precipitate generated in the step (2), removing the supernatant, and washing with hot ethanol for 10 times to obtain the cobalt-containing precursor.
(4) And (4) drying the precursor containing cobalt obtained in the step (3) in a 60 ℃ oven for 2 h.
(5) Under the condition of continuous stirring, 0.16g of a cobalt-containing precursor and 0.2g of Thioacetamide (TAA) were added to 80mL of anhydrous ethanol, and the mixture was stirred at 700rpm for 40 minutes to completely dissolve the cobalt-containing precursor and the thioacetamide.
(6) And (5) transferring the solution in the step (5) into a liner of a reaction kettle, putting the liner into a stainless steel reaction kettle, and keeping the temperature constant for 6 hours at 120 ℃ to obtain CoS.
(7) The crystallinity of the CoS is improved by calcining the CoS for 5h at 450 ℃.
Secondly, compounding cobalt sulfide and carbon nanotubes:
(8) adding 0.4g of carbon nano tube into 200mL of 3mol/L dilute nitric acid, carrying out ultrasonic treatment for 1h, carrying out continuous stirring under the condition that the rotating speed is 500rpm, heating the solution to 60 ℃, and keeping the temperature for 4 h.
(9) And (3) carrying out suction filtration on the solution obtained in the step (8) to obtain the carbon nano tube, adding the carbon nano tube into 200mL of concentrated nitric acid (65% -68%), continuously stirring at the rotation speed of 700rpm, heating the solution to 60 ℃, keeping the temperature for 4h, diluting the reacted solution by 10 times, carrying out suction filtration and washing, and obtaining the oxidized carbon nano tube.
(10) And (4) freeze-drying the oxidized carbon nano tube obtained in the step (9) for 48 hours.
(11) And (3) under the condition of continuous stirring at the rotating speed of 600rpm, adding 0.08g of CoS calcined in the step (7) into 50mL of absolute ethyl alcohol, adding 5mg of oxidized carbon nano tubes into the solution, and continuously stirring for 40 min.
(12) And (4) carrying out suction filtration on the solution stirred in the step (11), and carrying out freeze drying to obtain the carbon nanotube composite CoS negative electrode material.
Fig. 1 is an SEM image of the cobalt-containing precursor prepared in example 1. As can be seen from FIG. 1, the precursor obtained by this method is rod-shaped, and the length of the precursor is mostly concentrated in about 1-2 μm.
FIG. 2 is a TEM image of CoS prepared in example 1. As can be seen from FIG. 2, the thickness of the rod-like CoS obtained by this method is mostly concentrated in the range of 40 to 60 nm.
Fig. 3 is an SEM image of CoS of the composite carbon nanotube prepared in example 1. It can be seen from FIG. 3 that the carbon nanotubes and the rod-shaped CoS are uniformly combined.
Example 2
A preparation method of a high-capacity carbon nanotube composite CoS negative electrode material for a lithium ion battery comprises the following steps:
firstly, preparing cobalt sulfide:
(1) 4g of polyvinylpyrrolidone (PVP) were dissolved homogeneously in 200mL of absolute ethanol with stirring at 700rpm until the solution became clear.
(2) Under stirring at 500rpm, 1.5g of cobalt acetate tetrahydrate (Co (CH)3COO)2·4H2O) is added into the solution, the mixture is continuously stirred for 30min at room temperature, and is kept stand for 40h after cobalt acetate is uniformly dispersed, so that precursor sediment containing cobalt is obtained.
(3) And (3) centrifuging the solution of the precipitate generated in the step (2), removing the supernatant, and washing with hot ethanol for 15 times to obtain the cobalt-containing precursor.
(4) And (4) drying the precursor containing cobalt obtained in the step (3) in an oven at 80 ℃ for 2 h.
(5) Under the condition of continuous stirring, 0.18g of a cobalt-containing precursor and 0.25g of Thioacetamide (TAA) were added to 80mL of anhydrous ethanol, and the mixture was stirred at 600rpm for 40 minutes to completely dissolve the cobalt-containing precursor and the thioacetamide.
(6) And (5) transferring the solution in the step (5) into a liner of a reaction kettle, putting the liner into a stainless steel reaction kettle, and keeping the temperature constant for 6 hours at 110 ℃ to obtain CoS.
(7) The CoS is calcined for 6h at 500 ℃ to improve the crystallinity of the CoS.
Secondly, compounding cobalt sulfide and carbon nanotubes:
(8) adding 0.4g of carbon nano tube into 200mL of 2mol/L dilute nitric acid, carrying out ultrasonic treatment for 1h, carrying out continuous stirring under the condition that the rotating speed is 700rpm, heating the solution to 80 ℃, and keeping the temperature for 2 h.
(9) And (3) carrying out suction filtration on the solution obtained in the step (8) to obtain the carbon nano tube, adding the carbon nano tube into 200mL of concentrated nitric acid (65% -68%), continuously stirring at the rotation speed of 400rpm, heating the solution to 80 ℃, keeping the temperature for 4h, diluting the reacted solution by 8 times, carrying out suction filtration and washing, and obtaining the oxidized carbon nano tube.
(10) And (4) freeze-drying the oxidized carbon nano tube obtained in the step (9) for 50 h.
(11) And (3) under the condition of continuous stirring at the rotating speed of 800rpm, adding 0.1g of CoS calcined in the step (7) into 50mL of absolute ethyl alcohol, adding 5mg of oxidized carbon nano tube into the solution, and continuously stirring for 50 min.
(12) And (4) carrying out suction filtration on the solution stirred in the step (11), and carrying out freeze drying to obtain the carbon nanotube composite CoS negative electrode material.
Example 3
A preparation method of a high-capacity carbon nanotube composite CoS negative electrode material for a lithium ion battery comprises the following steps:
firstly, preparing cobalt sulfide:
(1) 4g of polyvinylpyrrolidone (PVP) was dissolved homogeneously in 200mL of absolute ethanol with stirring at 400rpm until the solution became clear.
(2) Under stirring at 700rpm, 1g of cobalt acetate tetrahydrate (Co (CH)3COO)2·4H2O) is added into the solution, the mixture is continuously stirred for 30min at room temperature, and is kept stand for 48h after cobalt acetate is uniformly dispersed, so as to obtain a cobalt-containing precursor precipitate.
(3) And (3) centrifuging the solution of the precipitate generated in the step (2), removing the supernatant, and washing with hot ethanol for 15 times to obtain the cobalt-containing precursor.
(4) And (4) drying the precursor containing cobalt obtained in the step (3) in an oven at 60 ℃ for 4 h.
(5) Under the condition of continuous stirring, 0.14g of a cobalt-containing precursor and 0.2g of Thioacetamide (TAA) were added to 80mL of anhydrous ethanol, and the mixture was stirred at 600rpm for 40 minutes to completely dissolve the cobalt-containing precursor and the thioacetamide.
(6) And (5) transferring the solution in the step (5) into a liner of a reaction kettle, putting the liner into a stainless steel reaction kettle, and keeping the temperature constant for 6 hours at 140 ℃ to obtain CoS.
(7) The crystallinity of the CoS is improved by calcining the CoS for 4h at 600 ℃.
Secondly, compounding cobalt sulfide and carbon nanotubes:
(8) adding 0.2g of carbon nano tube into 200mL of 1mol/L dilute nitric acid, carrying out ultrasonic treatment for 1h, carrying out continuous stirring under the condition that the rotating speed is 400rpm, heating the solution to 70 ℃, and keeping the temperature for 3 h.
(9) And (3) carrying out suction filtration on the solution obtained in the step (8) to obtain the carbon nano tube, adding the carbon nano tube into 200mL of concentrated nitric acid (65% -68%), continuously stirring at the rotation speed of 700rpm, heating the solution to 60 ℃, keeping the temperature for 6h, diluting the reacted solution by 10 times, carrying out suction filtration and washing, and obtaining the oxidized carbon nano tube.
(10) And (4) freeze-drying the oxidized carbon nano tube obtained in the step (9) for 52 hours.
(11) And (3) under the condition of continuous stirring at the rotating speed of 700rpm, adding 0.09g of CoS calcined in the step (7) into 50mL of absolute ethyl alcohol, adding 8mg of oxidized carbon nano tube into the solution, and continuously stirring for 60 min.
(12) And (4) carrying out suction filtration on the solution stirred in the step (11), and carrying out freeze drying to obtain the carbon nanotube composite CoS negative electrode material.
Example 4
A preparation method of a high-capacity carbon nanotube composite CoS negative electrode material for a lithium ion battery comprises the following steps:
firstly, preparing cobalt sulfide:
(1) 5g of polyvinylpyrrolidone (PVP) were dissolved homogeneously in 200mL of absolute ethanol with stirring at 600rpm until the solution became clear.
(2) 2g of cobalt acetate tetrahydrate (Co (CH) was stirred at 400rpm3COO)2·4H2O) is added into the solution, the mixture is continuously stirred for 35min at room temperature, and is kept stand for 50h after cobalt acetate is uniformly dispersed, so that precursor sediment containing cobalt is obtained.
(3) And (3) centrifuging the solution of the precipitate generated in the step (2), removing the supernatant, and washing with hot ethanol for 20 times to obtain the cobalt-containing precursor.
(4) And (4) drying the precursor containing cobalt obtained in the step (3) in an oven at 60 ℃ for 4 h.
(5) Under the condition of continuous stirring, 0.16g of a cobalt-containing precursor and 0.2g of Thioacetamide (TAA) were added to 80mL of anhydrous ethanol, and the mixture was stirred at 600rpm for 35 minutes to completely dissolve the cobalt-containing precursor and the thioacetamide.
(6) And (5) transferring the solution in the step (5) into a liner of a reaction kettle, putting the liner into a stainless steel reaction kettle, and keeping the temperature constant for 8 hours at 150 ℃ to obtain CoS.
(7) The CoS is calcined for 6h at 400 ℃ to improve the crystallinity of the CoS.
Secondly, compounding cobalt sulfide and carbon nanotubes:
(8) adding 0.6g of carbon nano tube into 200mL of 3mol/L dilute nitric acid, carrying out ultrasonic treatment for 1h, carrying out continuous stirring under the condition that the rotating speed is 600rpm, heating the solution to 60 ℃, and keeping the temperature for 4 h.
(9) And (3) carrying out suction filtration on the solution obtained in the step (8) to obtain the carbon nano tube, adding the carbon nano tube into 200mL of concentrated nitric acid (65% -68%), continuously stirring at the rotation speed of 600rpm, heating the solution to 70 ℃, keeping the temperature for 5h, diluting the reacted solution by 12 times, carrying out suction filtration and washing, and obtaining the oxidized carbon nano tube.
(10) And (4) freeze-drying the oxidized carbon nano tube obtained in the step (9) for 50 h.
(11) And (3) under the condition of continuous stirring at the rotating speed of 600rpm, adding 0.1g of CoS calcined in the step (7) into 50mL of absolute ethyl alcohol, adding 8mg of oxidized carbon nano tube into the solution, and continuously stirring for 50 min.
(12) And (4) carrying out suction filtration on the solution stirred in the step (11), and carrying out freeze drying to obtain the carbon nanotube composite CoS negative electrode material.
Example 5
A preparation method of a high-capacity carbon nanotube composite CoS negative electrode material for a lithium ion battery comprises the following steps:
firstly, preparing cobalt sulfide:
(1) 5g of polyvinylpyrrolidone (PVP) were dissolved homogeneously in 200mL of absolute ethanol with stirring at 700rpm until the solution became clear.
(2) Under stirring at 400rpm, 1.7g of cobalt acetate tetrahydrate (Co (CH)3COO)2·4H2O) is added into the solution, the mixture is continuously stirred for 30min at room temperature, and is kept stand for 48h after cobalt acetate is uniformly dispersed, so as to obtain a cobalt-containing precursor precipitate.
(3) And (3) centrifuging the solution of the precipitate generated in the step (2), removing the supernatant, and washing with hot ethanol for 20 times to obtain the cobalt-containing precursor.
(4) And (4) drying the precursor containing cobalt obtained in the step (3) in an oven at 60 ℃ for 6 h.
(5) Under the condition of continuous stirring, 0.17g of a cobalt-containing precursor and 0.23g of Thioacetamide (TAA) were added to 80mL of anhydrous ethanol, and the mixture was stirred at 800rpm for 40 minutes to completely dissolve the cobalt-containing precursor and the thioacetamide.
(6) And (5) transferring the solution in the step (5) into a liner of a reaction kettle, putting the liner into a stainless steel reaction kettle, and keeping the temperature constant for 6 hours at 160 ℃ to obtain CoS.
(7) The CoS is calcined for 6h at 600 ℃ to improve the crystallinity of the CoS.
Secondly, compounding cobalt sulfide and carbon nanotubes:
(8) adding 0.4g of carbon nano tube into 200mL of 2mol/L dilute nitric acid, carrying out ultrasonic treatment for 1h, carrying out continuous stirring under the condition that the rotating speed is 600rpm, heating the solution to 60 ℃, and keeping the temperature for 4 h.
(9) And (3) carrying out suction filtration on the solution obtained in the step (8) to obtain the carbon nano tube, adding the carbon nano tube into 200mL of concentrated nitric acid (65% -68%), continuously stirring at the rotation speed of 600rpm, heating the solution to 80 ℃, keeping the temperature for 4h, diluting the reacted solution by 8 times, carrying out suction filtration and washing, and obtaining the oxidized carbon nano tube.
(10) And (4) freeze-drying the oxidized carbon nano tube obtained in the step (9) for 48 hours.
(11) And (3) under the condition of continuous stirring at the rotating speed of 600rpm, adding 0.1g of CoS calcined in the step (7) into 50mL of absolute ethyl alcohol, adding 10mg of oxidized carbon nano tube into the solution, and continuously stirring for 50 min.
(12) And (4) carrying out suction filtration on the solution stirred in the step (11), and carrying out freeze drying to obtain the carbon nanotube composite CoS negative electrode material.
Example 6
A preparation method of a high-capacity carbon nanotube composite CoS negative electrode material for a lithium ion battery comprises the following steps:
firstly, preparing cobalt sulfide:
(1) under stirring at 600rpm, 3g of polyvinylpyrrolidone (PVP) was dissolved homogeneously in 200mL of absolute ethanol until the solution became clear.
(2) Under stirring at 700rpm, 1.28g of cobalt acetate tetrahydrate (Co (CH)3COO)2·4H2O) is added into the solution, the mixture is continuously stirred for 30min at room temperature, and is kept stand for 45h after cobalt acetate is uniformly dispersed, so that precursor sediment containing cobalt is obtained.
(3) And (3) centrifuging the solution of the precipitate generated in the step (2), removing the supernatant, and washing with hot ethanol for 10 times to obtain the cobalt-containing precursor.
(4) And (4) drying the precursor containing cobalt obtained in the step (3) in a 60 ℃ oven for 2 h.
(5) Under the condition of continuous stirring, 0.18g of a cobalt-containing precursor and 0.25g of Thioacetamide (TAA) were added to 80mL of anhydrous ethanol, and the mixture was stirred at 600rpm for 40 minutes to completely dissolve the cobalt-containing precursor and the thioacetamide.
(6) And (5) transferring the solution in the step (5) into a liner of a reaction kettle, putting the liner into a stainless steel reaction kettle, and keeping the temperature constant for 5 hours at 150 ℃ to obtain CoS.
(7) The CoS is calcined for 6h at 500 ℃ to improve the crystallinity of the CoS.
Secondly, compounding cobalt sulfide and carbon nanotubes:
(8) adding 0.6g of carbon nano tube into 200mL of 2mol/L dilute nitric acid, carrying out ultrasonic treatment for 1h, carrying out continuous stirring under the condition that the rotating speed is 700rpm, heating the solution to 80 ℃, and keeping the temperature for 4 h.
(9) And (3) carrying out suction filtration on the solution obtained in the step (8) to obtain a carbon nano tube, adding the carbon nano tube into 200mL of concentrated nitric acid (65% -68%), heating the solution to 60 ℃ under the condition of continuously stirring at the rotating speed of 400rpm, keeping the temperature for 6h, diluting the reacted solution by 12 times, carrying out suction filtration and washing, and obtaining the oxidized carbon nano tube.
(10) And (4) freeze-drying the oxidized carbon nano tube obtained in the step (9) for 48 hours.
(11) And (3) under the condition of continuous stirring at the rotating speed of 800rpm, adding 0.1g of CoS calcined in the step (7) into 50mL of absolute ethyl alcohol, adding 10mg of oxidized carbon nano tube into the solution, and continuously stirring for 50 min.
(12) And (4) carrying out suction filtration on the solution stirred in the step (11), and carrying out freeze drying to obtain the carbon nanotube composite CoS negative electrode material.
Comparative example
(1) Under stirring at 500rpm, 3g of polyvinylpyrrolidone (PVP) was dissolved uniformly in 200mL of absolute ethanol until the solution became clear.
(2) Under stirring at 600rpm, 1.28g of cobalt acetate tetrahydrate (Co (CH)3COO)2·4H2O) is added into the solution, the mixture is continuously stirred for 20min at room temperature, and is kept stand for 48h after cobalt acetate is uniformly dispersed, so as to obtain a cobalt-containing precursor precipitate.
(3) And (3) centrifuging the solution of the precipitate generated in the step (2), removing the supernatant, and washing with hot ethanol for 10 times to obtain the cobalt-containing precursor.
(4) And (4) drying the precursor containing cobalt obtained in the step (3) in a 60 ℃ oven for 2 h.
(5) Under the condition of continuous stirring, 0.16g of a cobalt-containing precursor and 0.2g of Thioacetamide (TAA) were added to 80mL of anhydrous ethanol, and the mixture was stirred at 700rpm for 40 minutes to completely dissolve the cobalt-containing precursor and the thioacetamide.
(6) And (5) transferring the solution in the step (5) into a liner of a reaction kettle, putting the liner into a stainless steel reaction kettle, and keeping the temperature constant for 6 hours at 120 ℃ to obtain CoS.
(7) And calcining CoS for 5h at 450 ℃ to obtain the CoS negative electrode material.
Test example
(1) Assembling a half cell: the carbon nanotube composite CoS negative electrode material prepared in example 1 and the negative electrode material obtained in the comparative example are respectively slurried and coated with acetylene black and PVDF according to the mass ratio of 8:1:1, and a half cell is assembled by taking a metal lithium sheet as a negative electrode.
(2) And (3) charge and discharge test: the carbon nanotube-composited CoS negative electrode material prepared in example 1 and the negative electrode material obtained in the comparative example were charged and discharged at a constant current of 80 mA/g.
Fig. 4 is a graph showing the relationship between the specific discharge capacity and the number of cycles of the lithium ion battery manufactured by the CoS negative electrode material of the composite carbon nanotube prepared in example 1 and the CoS negative electrode material prepared in the comparative example. It can be seen from fig. 4 that the first discharge capacity of the negative electrode material prepared in example 1 is 980.0mAh/g, the first coulomb efficiency is 78%, and the capacity fading condition is significantly improved. The first discharge capacity of the negative electrode material prepared by the comparative example is 892.4mAh/g, and the first-turn coulombic efficiency is 72%. The electrochemical performance of the CoS negative electrode material compounded with the carbon nano tube is more excellent.
In addition, the CoS negative electrode material of the composite carbon nanotube obtained in the embodiments 2-6, acetylene black and PVDF are respectively slurried and coated according to the mass ratio of 8:1:1, and a half cell is assembled by taking a metal lithium sheet as a negative electrode; then, charging and discharging tests are carried out under the constant current of 80mA/g, and the following results are obtained through detection:
the first discharge capacity of the negative electrode material prepared in example 2 is 925.1mAh/g, and the first coulomb efficiency is 75%.
The first discharge capacity of the negative electrode material prepared in example 3 is 894.5mAh/g, and the first coulomb efficiency is 74%.
The first discharge capacity of the negative electrode material prepared in example 4 is 884.4mAh/g, and the first coulomb efficiency is 76%.
The first discharge capacity of the negative electrode material prepared in example 5 is 904.6mAh/g, and the first coulomb efficiency is 73%.
The first discharge capacity of the negative electrode material prepared in example 6 was 917.7mAh/g, and the first coulomb efficiency was 78%.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (9)
1. A preparation method of a high-capacity carbon nanotube composite cobalt sulfide cathode material for a lithium ion battery is characterized by comprising the following steps of:
(A) adding carbon nanotubes into dilute nitric acid, performing ultrasonic treatment, continuously stirring at the rotation speed of 400-700 rpm, and heating the solution;
(B) carrying out suction filtration on the solution obtained in the step (A) to obtain a carbon nano tube, adding the carbon nano tube into concentrated nitric acid, continuously stirring at the rotating speed of 400-700 rpm, heating the solution, diluting the reacted solution, carrying out suction filtration and washing to obtain an oxidized carbon nano tube;
(C) freeze-drying the oxidized carbon nanotubes obtained in step (B);
(D) adding the calcined cobalt sulfide into absolute ethyl alcohol under the condition of continuous stirring at the rotating speed of 600-800 rpm, adding the oxidized carbon nano tube into the solution, and continuously stirring for 40-60 min;
(E) carrying out suction filtration on the solution stirred in the step (D), and freeze-drying to obtain the carbon nano tube composite cobalt sulfide negative electrode material;
the preparation method of the calcined cobalt sulfide in the step (D) comprises the following steps:
(1) uniformly dissolving polyvinylpyrrolidone in absolute ethyl alcohol under the stirring condition that the rotating speed is 400-700 rpm until the solution becomes clear;
(2) adding cobalt acetate tetrahydrate into the solution in the step (1) under the stirring condition of the rotating speed of 400-700 rpm, continuously stirring for 20-40 min at room temperature, standing for 40-50 h after the cobalt acetate is uniformly dispersed, and obtaining a cobalt-containing precursor precipitate;
(3) centrifuging the solution of the precipitate generated in the step (2), removing supernatant, and washing with hot ethanol for 10-20 times to obtain a cobalt-containing precursor;
(4) drying the cobalt-containing precursor obtained in the step (3);
(5) under the condition of continuous stirring, adding a cobalt-containing precursor and thioacetamide in a certain proportion into absolute ethyl alcohol, and continuously stirring for 30-40 min under the condition that the stirring speed is 600-800 rpm to completely dissolve the cobalt-containing precursor and the thioacetamide;
(6) transferring the solution in the step (5) into a liner of a reaction kettle, putting the liner into a stainless steel reaction kettle, and keeping the temperature at 110-160 ℃ for 5-8 h to obtain CoS;
(7) and calcining CoS at 400-600 ℃ for 4-6 h to improve the crystallinity of the CoS.
2. The preparation method of the high-capacity carbon nanotube composite cobalt sulfide negative electrode material for the lithium ion battery according to claim 1, characterized in that:
the heating condition in the step (A) is heating to 60-80 ℃ and keeping the temperature for 2-4 h;
the concentration of the carbon nano tubes in the solution in the step (A) is 1-3 g/L.
3. The preparation method of the high-capacity carbon nanotube composite cobalt sulfide negative electrode material for the lithium ion battery according to claim 1, characterized in that:
the concentration of the dilute nitric acid in the step (A) is 1-3 mol/L;
the concentrated nitric acid in the step (B) is 65-68 percent.
4. The preparation method of the high-capacity carbon nanotube composite cobalt sulfide negative electrode material for the lithium ion battery according to claim 1, characterized in that:
heating to 60-80 ℃ and keeping the temperature for 4-6 h;
diluting the solution after the reaction in the step (B) to 8-12 times of the solution after the reaction;
and (C) the freeze drying time in the step (C) is 48-52 h.
5. The preparation method of the high-capacity carbon nanotube composite cobalt sulfide negative electrode material for the lithium ion battery according to claim 1, characterized in that:
the concentration of cobalt sulfide in the solution in the step (D) is 1.6-2 g/L;
the mass ratio of the cobalt sulfide to the oxidized carbon nano tube is (16-20): (1-2).
6. The preparation method of the high-capacity carbon nanotube composite cobalt sulfide negative electrode material for the lithium ion battery according to claim 1, characterized in that:
the concentration of polyvinylpyrrolidone in the solution in the step (1) is 15-25 g/L;
the mass ratio of the cobalt acetate tetrahydrate to the polyvinylpyrrolidone in the step (2) is (1-2): (3-5).
7. The preparation method of the high-capacity carbon nanotube composite cobalt sulfide negative electrode material for the lithium ion battery according to claim 1, characterized in that:
drying for 2-6 h at the temperature of 60-80 ℃ in the drying condition in the step (4);
the mass ratio of the cobalt-containing precursor to thioacetamide in the step (5) is (7-9): (10-12.5).
8. A high-capacity carbon nanotube composite cobalt sulfide negative electrode material for a lithium ion battery is characterized by being prepared by the preparation method of any one of claims 1 to 7.
9. Use of the high capacity carbon nanotube composite cobalt sulfide negative electrode material for lithium ion batteries of claim 8 in the manufacture of lithium ion batteries.
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