CN109378450B - Hierarchical porous ZnFe2O4Negative electrode material of/C lithium ion battery and preparation method thereof - Google Patents

Hierarchical porous ZnFe2O4Negative electrode material of/C lithium ion battery and preparation method thereof Download PDF

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CN109378450B
CN109378450B CN201811074602.6A CN201811074602A CN109378450B CN 109378450 B CN109378450 B CN 109378450B CN 201811074602 A CN201811074602 A CN 201811074602A CN 109378450 B CN109378450 B CN 109378450B
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lithium ion
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CN109378450A (en
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郭兴忠
冯道言
杨辉
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Zhejiang University ZJU
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Abstract

The invention provides a hierarchical porous ZnFe2O4Firstly, ZnFe is put into the preparation method of the negative electrode material of the/C lithium ion battery2O4Adding the mixture into Tris-HCl buffer solution, performing ultrasonic treatment for 10 +/-1 min, and stirring for 20-40 min to obtain dispersion liquid; secondly, adding dopamine into the obtained dispersion liquid, and magnetically stirring for 24 +/-2 hours to obtain suspension; placing a black precipitate obtained by centrifuging the obtained suspension in a drying oven at 40-60 ℃ for drying for 48 +/-2 hours to obtain a black sample; and finally, placing the obtained black sample in a tube furnace, heating to 100-200 ℃ at a heating rate of 2-7 ℃/min under the protection of argon, preserving heat for 60-120 min, heating to 400-700 ℃ at a heating rate of 2-7 ℃/min, preserving heat for 100-300 min, and finally obtaining the carbon-coated hierarchical porous ZnFe2O4An active electrode material.

Description

Hierarchical porous ZnFe2O4Negative electrode material of/C lithium ion battery and preparation method thereof
Technical Field
The invention relates to the field of electrochemistry, in particular to a hierarchical porous ZnFe2O4a/C lithium ion battery cathode material and a preparation method thereof.
Background
In recent years, with the gradual deterioration of ecological environment and the gradual shortage of traditional fossil energy, the development of new green energy becomes a primary target of countries in the world. Chemical power sources have received much attention both at home and abroad as a new energy source. Due to the ever-increasing demand for energy conversion and storage, lithium ion batteries have received great attention from portable electronic devices to electric vehicles due to their superior energy density over other rechargeable batteries, from portable electronic devices toIn electric vehicles, lithium ion batteries have received great attention because they have higher energy density than other rechargeable batteries. The negative electrode material is an important factor influencing the performance of the lithium ion battery. Currently, graphite is widely used as a negative electrode material of a lithium ion battery due to a series of advantages of rich sources, low price, long cycle life and the like. However, graphite has a low theoretical capacity (372mAh g)-1) And potential safety hazards, and the like, so more and more researchers are invested in the research of novel cathode materials. ZnFe2O4The anode material has the advantages of high theoretical specific capacity, low price and the like, is one of the most potential anode materials, and attracts the attention of a large number of researchers.
Existing ZnFe2O4The preparation method usually comprises hydrothermal, solvent thermal, high-temperature radiation, electrostatic spinning and other methods, and has the problems of complex equipment, harsh experimental conditions, non-uniform products and poor repeatability, so that the preparation method is not suitable for continuous industrial production.
The mechanism that the surface coated carbon layer can improve the electrochemical performance of the material is as follows: firstly, the existence of the carbon layer can provide channels for ions and electrons, and the conductivity of the material is enhanced; secondly, the agglomeration among electrode material particles can be inhibited, and the utilization rate of active substances is improved. The carbon layer acts as a relief layer to relieve the material from stresses due to volume expansion and contraction.
The prior ZnFe2O4the/C production method generally uses glucose as a carbon source, the carbon conversion efficiency is low, and the carbon layer formed is not uniform.
In view of the above, further improvements to the prior art are needed.
Disclosure of Invention
The invention aims to solve the technical problem of providing a hierarchical porous ZnFe2O4Negative electrode material of/C lithium ion battery, preparation method of negative electrode material, and prepared hierarchical porous ZnFe2O4the/C active electrode material can be used as a negative electrode material of a lithium ion battery.
In order to solve the technical problem, the invention provides a hierarchical porous ZnFe2O4The preparation method of the/C lithium ion battery negative electrode material comprises the following steps:
s1, mixing ZnFe2O4Adding into Tris-HCl buffer (pH 8.5), ultrasonic treating for 10 +/-1 min, and stirring for 20-40 min (to obtain ZnFe2O4Uniformly dispersing) to obtain a dispersion liquid;
the ZnFe2O4The mass-to-volume ratio of the buffer solution to Tris-HCl buffer solution is 5 mg: 1 ml;
s2, adding dopamine into the dispersion liquid obtained in the step S1, and magnetically stirring for 24 +/-2 hours to obtain suspension liquid;
ZnFe in the step S12O4The mass ratio of the dopamine to the dopamine is 5-9: 1 (optimally 5: 1);
s3, centrifuging the suspension obtained in the step S2 (the centrifugal rotation speed is 10000r/min, and the time is 10min), and then drying the obtained black precipitate in an oven at the temperature of 40-60 ℃ for 48 +/-2 h to obtain a black sample;
s4, placing the black sample obtained in the step S3 in a tube furnace, heating to 100-200 ℃ at a heating rate of 2-7 ℃/min under the protection of argon, preserving heat for 60-120 min, heating to 400-700 ℃ at a heating rate of 2-7 ℃/min, preserving heat for 100-300 min, and finally obtaining the hierarchical porous ZnFe2O4Negative electrode material of/C lithium ion battery (i.e. carbon-coated hierarchical porous ZnFe)2O4/C active electrode material).
The invention is a hierarchical porous ZnFe2O4The improvement of the preparation method of the/C lithium ion battery negative electrode material:
s1, mixing ZnFe2O4Adding into Tris-HCl buffer (pH 8.5), ultrasonic treating for 10min, and stirring for 30min (to obtain ZnFe solution)2O4Uniformly dispersing) to obtain a dispersion liquid;
the ZnFe2O4The mass-to-volume ratio of the buffer solution to Tris-HCl buffer solution is 5 mg: 1 ml;
s2, adding dopamine into the dispersion liquid obtained in the step S1, and magnetically stirring for 24 hours to obtain suspension;
ZnFe in the step S12O4The mass ratio of the dopamine to the dopamine is 5: 1;
s3, centrifuging the suspension obtained in the step S2 for 3-5 times (the rotating speed of each centrifugation is 10000r/min, the time is 10min), and then placing the obtained black precipitate in an oven at 40-60 ℃ for drying for 48 +/-2 h to obtain a black sample;
s4, placing the black sample obtained in the step S3 in a tube furnace, heating to 150 ℃ at a heating rate of 5 ℃/min under the protection of argon, preserving heat for 60min, heating to 550 ℃ at a heating rate of 5 ℃/min, preserving heat for 180min, and finally obtaining the hierarchical porous ZnFe2O4Negative electrode material of/C lithium ion battery (i.e. carbon-coated hierarchical porous ZnFe)2O4/C active electrode material).
The invention is a hierarchical porous ZnFe2O4The preparation method of the/C lithium ion battery negative electrode material is further improved as follows:
the ZnFe2O4The preparation method of (1) comprises the following steps;
A) adding deionized water into glycerol, and magnetically stirring until the deionized water and the glycerol are uniformly mixed to obtain a solution I;
the volume ratio of the deionized water to the glycerol is 0.3-0.6: 1;
B) adding polyacrylic acid into the solution I obtained in the step A), and fully stirring until the polyacrylic acid is completely dispersed and dissolved to obtain a solution II;
the mass ratio of the deionized water to the polyacrylic acid in the step A) is 0.2-0.9: 1;
C) adding a zinc source and an iron source serving as precursors into the solution II obtained in the step B), and stirring until the zinc source and the iron source are completely hydrolyzed to obtain a clear and transparent solution III; the molar ratio of the deionized water to the zinc source in the step A) is 15-45: 1;
the molar ratio of the zinc source to the iron source is 0.5: 1;
D) adding a gel accelerator into the solution III obtained in the step C), and stirring for 40-60 min to obtain sol;
the volume ratio of the deionized water to the gel promoter in the step A) is 0.5-2.5: 1;
E) sealing the sol obtained in the step D), and placing the sol in an oven at the temperature of 40-60 ℃ for gelling for 48 +/-2 hours to obtain block gel;
F) putting the block gel obtained in the step E) into a drying oven at 40-60 ℃ for drying for 48 +/-2 hours to obtain block xerogel;
G) putting the block xerogel obtained in the step F) into a muffle furnace, heating to 400-700 ℃ at a heating rate of 0.5-5 ℃/min, and preserving the temperature for 100-300 min to obtain ZnFe2O4(i.e., hierarchical porous ZnFe)2O4Material).
The invention is a hierarchical porous ZnFe2O4The preparation method of the/C lithium ion battery negative electrode material is further improved as follows:
the molecular weight of the polyacrylic acid adopted in the step B) is 3000-10000 (the molecular weight of the polyacrylic acid is 3000, 5000, 50000 or 10000).
The invention is a hierarchical porous ZnFe2O4The preparation method of the/C lithium ion battery negative electrode material is further improved as follows:
the zinc source in the step C) is ZnCl2Or Zn (NO)3)2·6H2O, iron source being FeCl2·4H2O or Fe (NO)3)2·6H2O。
The preparation method of the hierarchical porous ZnFe2O4/C lithium ion battery anode material is further improved as follows:
the gel accelerator in the step D) is added in a dropwise manner, and the temperature is not more than 60 ℃ in the dropwise process.
The invention is a hierarchical porous ZnFe2O4The preparation method of the/C lithium ion battery negative electrode material is further improved as follows:
the gel accelerator used in step D) is propylene oxide or formamide.
Note: the preparation method of Tris-HCl buffer (pH 8.5) in step S1 is as follows:
each 500ml of Tris-HCl buffer solution is prepared by mixing 250ml of 0.1mol/L Tris hydroxymethyl aminomethane solution and 73.5ml of 0.1mol/L hydrochloric acid, and then adding deionized water to dilute to 500 ml.
In order to solve the technical problem, the invention also provides a hierarchical porous ZnFe2O4/C lithium ion battery anode material prepared by the method.
Compared with the prior art, the invention has the following technical advantages:
1) the invention adopts a phase separating agent (polyacrylic acid) to be an active material (ZnFe)2O4) Micron-sized macropores are introduced, so that the flow of electrolyte and the Li are facilitated+Transporting;
2) active material (ZnFe) obtained by the invention2O4) The structure of the hollow framework improves the active electrode material (ZnFe) prepared2O4The specific surface area of the/C) promotes the contact of the electrolyte and the active electrode, thereby being beneficial to the proceeding of electrochemical reaction;
3) the invention improves the active material (ZnFe) through the in-situ loading of the active carbon2O4) The conductivity of the material is favorable for the transportation of electrons, and the electrochemical reaction rate is accelerated;
4) the nanometer ZnFe prepared by the invention2O4Small particle size and thus shortening of Li+A transport path for further accelerating the electrochemical reaction;
5) according to the invention, the obtained block xerogel (zinc-iron hydroxide) is subjected to heat treatment to form a macroporous-mesoporous-microporous hierarchical porous structure so as to relieve the volume expansion effect generated in the charging and discharging process;
6) the invention adopts a sol-gel method to prepare ZnFe2O4With the conventional ZnFe2O4Compared with the preparation method (hydrothermal method, solvent thermal method, high-temperature radiation method, electrostatic spinning and the like), the preparation method has mild preparation conditions (the mild condition means that the synthesis of the zinc salt and the iron salt is completed at room temperature (25-35 ℃), and heating or other treatment is not needed), and can realize continuous industrial production;
7) the invention adopts dopamine as a carbon source to prepare ZnFe2O4The thickness of a carbon layer of the/C is uniform and controllable, and the conversion rate of carbon is high;
8) the production process and equipment are simple, and industrialization is easy to realize; the production process does not produce harmful substances.
Drawings
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
FIG. 1 shows a physical representation (a) and a scanning electron micrograph (b) of the appearance of the bulk xerogel (zinc iron hydroxide) prepared in example 1-1, and ZnFe2O4Scanning electron micrograph (c) of (c), ZnFe2O4(ii) a scanning electron micrograph (d) of/C;
FIG. 2 shows ZnFe prepared in example 1-12O4And ZnFe2O4Nitrogen sorption graph (a) and pore size distribution (b) for/C;
FIG. 3 is a block xerogel (zinc iron hydroxide), ZnFe prepared in example 1-12O4And ZnFe2O4A macroporous pore size distribution diagram of/C;
FIG. 4 is ZnFe prepared for example 1-22O4TG-DTA plot of/C;
FIG. 5 is a block xerogel (zinc iron hydroxide), ZnFe prepared for example 1-22O4And ZnFe2O4XRD spectrum of/C;
FIG. 6 is the ZnFe prepared for example 1-22O4(ii) a projection electron micrograph of/C;
FIG. (a) is ZnFe2O4Low power transmission electron micrograph of/C; FIG. (b) is an enlarged schematic view of the area corresponding to the region marked in FIG. (a); FIG. (c) is an enlarged schematic view of the area corresponding to the region marked in FIG. (b); FIG. d is an enlarged view of the area corresponding to the region marked in FIG. b;
FIG. 7 is a ZnFe alloy prepared for examples 1-32O4And ZnFe2O4The current density of/C is 200mAg-1And (4) a charge and discharge performance diagram.
FIG. 8 shows ZnFe prepared in examples 1-32O4The current density of the/C is 1Ag-1The performance diagram of the charge-discharge cycle is shown below.
Detailed Description
The invention will be further described with reference to specific examples, but the scope of the invention is not limited thereto.
Example 1-1, hierarchical porous ZnFe2O4The preparation method of the/C lithium ion battery cathode material comprises the following steps of:
A) weighing 1.2mL of deionized water (0.067mol) and adding the deionized water into 2.4mL of glycerol, and magnetically stirring until the deionized water and the glycerol are uniformly mixed to obtain a solution I;
B) adding 2.5g of polyacrylic acid into the solution I obtained in the step A), wherein the molecular weight of the polyacrylic acid is 10000, and fully stirring until the polyacrylic acid is completely dispersed and dissolved to obtain a solution II (uniform solution);
note: the mass of 1.2mL of deionized water is 1.2 g;
C) adding ZnCl serving as a precursor into the solution II obtained in the step B)2(i.e., zinc source) 0.408g (0.0029mol) and FeCl2·4H2O (iron source) 1.192g (0.0058mol), and stirred until ZnCl was obtained2And FeCl2·4H2Completely hydrolyzing O to obtain a clear and transparent solution III;
at this time, deionized water and ZnCl are mixed2The molar ratio was 23.1:1(0.067: 0.0029);
a zinc source: the molar ratio of the iron source to the iron source is 1: 2;
D) dripping 0.5ml of propylene oxide serving as a gel accelerator into the solution III obtained in the step C) (the temperature in the dripping process is not more than 40 ℃), and stirring for 40min to obtain sol;
E) sealing the sol obtained in the step D), and placing the sol in a drying oven at 40 ℃ for gelling for 48 hours to obtain block gel;
F) drying the block gel obtained in the step E) in an oven at 40 ℃ for 48 hours to obtain block xerogel;
G) and F) placing the block xerogel obtained in the step F) into a muffle furnace, heating to 550 ℃ at a heating rate of 0.5 ℃/min, and preserving heat for 100min to obtain hierarchical porous ZnFe2O4A material;
the ZnFe obtained is shown in FIGS. 1 and 22O4Is a hollow framework structure, the size of macropores is 400nm, ZnFe2O4The size of a/C macropore is 300 nm; ZnFe2O4And ZnFe2O4the/C mesopores are all 30 nm;
H) weighing ZnFe obtained in the step F)2O4Adding 150mg of the mixture into 30ml Tris-HCl buffer (pH 8.5), ultrasonic treating for 10min, and stirring for 30min to ensure ZnFe2O4Dispersing uniformly to obtain a dispersion liquid;
Tris-HCl buffer (pH 8.5) was prepared by mixing 250ml of 0.1mol/L Tris solution with 73.5ml of 0.1mol/L hydrochloric acid and diluting to 500 ml.
I) Adding 30mg of dopamine in the step H), and magnetically stirring for 24 hours to obtain a suspension;
J) centrifuging the suspension obtained in the step I) for 3 times (wherein the rotating speed is 10000r/min each time and the time is 10min), and drying the obtained black precipitate in a drying oven at 40 ℃ for 48h to obtain a black sample;
K) putting the black sample obtained in the step J) into a tube furnace, heating to 150 ℃ at a heating rate of 5 ℃/min under the protection of argon, preserving heat for 60min, heating to 550 ℃ at a heating rate of 5 ℃/min, preserving heat for 180min, and finally obtaining the carbon-coated hierarchical porous ZnFe2O4An active electrode material.
The obtained ZnFe2O4The thickness of the/C carbon layer was uniform at 4.1nm, the loading of carbon was 9.4%, and the conversion of carbon was 56.4%. At a current density of 1A g-1After 400 cycles of charge and discharge under high current density, the discharge specific capacitance can keep 711mAhg-1At a current density of 200mAg-1At the current density after 100 cycles of charge-discharge cycle ZnFe2O4the/C still maintains good charge-discharge performance, and the specific charge capacitance is 962.3mAh g-1Specific discharge capacitance 969.2mAh g-1。
The degree of uniformity of the thickness of the carbon-impregnated layer was confirmed by transmission electron microscopy, and the conversion of carbon was calculated from thermogravimetry (9.4%/(30/(150 +30)) -56.4%).
Preparing the obtained block xerogel and ZnFe2O4、ZnFe2O4the/C scanning electron micrograph is shown in FIG. 1, the ZnFe prepared in this example2O4Has an average grain size of 10nm, ZnFe2O4ZnFe in/C2O4Has an average grain size of 16 nm; ZnFe2O4/C、ZnFe2O4The data for the specific surface area of the active material are: ZnFe2O4(40m2g-1),ZnFe2O4/C(29m2g-1)；
As can be seen from FIG. 2, ZnFe2O4Coating carbon to form ZnFe2O4The nitrogen adsorption after/C is reduced because of ZnFe coated by carbon2O4ZnFe in/C2O4The number of micropores between the nanoparticles is reduced, eventually leading to ZnFe2O4/C(29m2g-1) Specific surface area ratio of (1) ZnFe2O4(40m2g-1) Low.
From FIG. 3, it can be seen that the pore diameter of the bulk xerogel (zinc iron hydroxide) macropore is 800nm, ZnFe2O4The pore diameter of the macropore is 400nm, ZnFe2O4The pore diameter of the/C macropore is 300 nm.
Examples 1-2, the temperature at which step E, step F and step J in example 1 were dried in an oven was changed from 40 ℃ to 50 ℃, and the temperature during the dropping in step D was changed from not more than 40 ℃ to not more than 50 ℃, and the rest was the same as example 1.
The obtained ZnFe2O4Is a hollow framework structure, the size of the macropores is 420nm, ZnFe2O4The size of a/C macropore is 350 nm; the mesoporous of ZnFe2O4 is 35nm, and the mesoporous of ZnFe2O4/C is 32 nm;
the obtained ZnFe2O4The thickness of the/C carbon layer was uniform at 4nm, the loading of carbon was 9.2%, and the conversion of carbon was 55.2%. At a current density of 200mAg-1The specific capacity of discharge after 100 cycles of charge-discharge at the current density of 860mAh g-1. At a current density of 1Ag-1After 400 cycles of charge and discharge under high current density, the specific discharge capacity can keep 670mAh g-1。
ZnFe2O4/C、ZnFe2O4Active material ratioThe surface area data is: ZnFe2O4(42m2g-1),ZnFe2O4/C(28m2g-1)；
ZnFe can be calculated from the (311) crystal plane in FIG. 52O4Has an average grain size of 10nm, ZnFe2O4The average grain size of the/C grains was 16 nm.
Note: ZnFe2O4The average size is 10nm without carbon coating, and after steps H) to K) (secondary heat treatment with carbon coating), the particles become larger, in this case 16 nm.
As can be seen from FIG. 6, ZnFe2O4the/C is a polycrystalline structured nano-particle with an average size of 16 nm; ZnFe is known from FIG. 6, Panel (a)2O4the/C is a porous structure, the diffraction ring at the upper right corner of the graph b is a low-energy electron diffraction spot in the area of the graph b, and ZnFe is proved2O4the/C is a polycrystalline structure; in FIG. (c), ZnFe is marked by a broken line2O4ZnFe in/C2O4The average size of the crystal particles was 16nm, 0.292nm in the graph (d) is the interplanar spacing of (220), 0.481nm is the interplanar spacing of (111), the amorphous regions marked by dashed lines at the edges represent the carbon layer, and 4nm is the thickness of the carbon layer.
Examples 1-3 the amount of polyacrylic acid used in step B of example 1 was changed from 2.5g to 3.5g, and the balance was the same as in example 1.
The obtained ZnFe2O4Is a hollow framework structure, the size of macropores is 390nm, ZnFe2O4The size of a/C macropore is 280 nm; the mesoporous of ZnFe2O4 is 29nm, and the mesoporous of ZnFe2O4/C is 27 nm;
the obtained ZnFe2O4The thickness of the/C carbon layer was uniform at 4nm, the loading of carbon was 9.6%, and the conversion of carbon was 57.6%.
As can be seen from FIG. 7, the current density was 200mAg-1At the current density after 100 cycles of charge-discharge cycle ZnFe2O4the/C still maintains good charge-discharge performance, and the specific charge capacitance is 960.6mAh g-1Specific discharge capacitance 967.8mAh g-1。ZnFe2O4Has a specific charge capacitance of 275.8mAh g-1The specific discharge capacitance was 278.4mAh g-1Thus, it was proved that the carbon coating can improve the charge and discharge stability.
From FIG. 8, it can be seen that the current density was 1A g-1After 400 cycles of charge and discharge under high current density, the discharge specific capacitance can retain 716mAh g-1。
ZnFe2O4/C、ZnFe2O4The data for the specific surface area of the active material are: ZnFe2O4(32m2g-1),ZnFe2O4/C(25m2g-1)；
ZnFe2O4Has an average grain size of 13nm, ZnFe2O4The average grain size of the/C grains was 20 nm.
Example 2 preparation of ZnFe in example 1-12O4The method is changed into the following steps:
A) weighing 1mL (0.056mol) of deionized water, adding into 2mL of glycerol, and magnetically stirring until the mixture is uniformly mixed to obtain a solution I;
B) adding 2.5g of polyacrylic acid into the solution I obtained in the step A), wherein the molecular weight of the polyacrylic acid is 100000, and fully stirring until the polyacrylic acid is completely dispersed and dissolved to obtain a solution II (uniform solution);
C) adding Zn (NO) as a precursor into the solution II obtained in the step B)3)2·6H2O0.826 g (0.00278mol) and Fe (NO)3)2·6H2O1.60 g (0.00556mol), stirred until Zn (NO)3)2·6H2O and Fe (NO)3)2·6H2Completely hydrolyzing O to obtain a clear and transparent solution III;
at this time, deionized water and ZnCl are mixed2The molar ratio is 20.1: 1(0.056: 0.00278);
Zn(NO3)2·6H2o and Fe (NO)3)2·6H2The molar ratio of O is 1: 2;
D) dripping 1.5ml of formamide serving as a gel accelerator into the solution III obtained in the step C) (the temperature does not exceed 60 ℃ in the dripping process, and stirring for 60min to obtain sol;
E) sealing the sol obtained in the step D), and placing the sol in a drying oven at 40 ℃ for gelling for 48 hours to obtain block gel;
F) drying the block gel obtained in the step E) in an oven at 40 ℃ for 48 hours to obtain block xerogel;
G) and F) placing the block xerogel obtained in the step F) into a muffle furnace, heating to 550 ℃ at a heating rate of 0.5 ℃/min, and preserving heat for 100min to obtain hierarchical porous ZnFe2O4A material;
the remaining equivalents were the same as in examples 1-1;
the obtained ZnFe2O4Is of hollow skeleton structure, ZnFe2O4The average size of the crystal grains is 9nm, the size of macropores is 450nm, the size of mesopores is 28nm, ZnFe2O4The specific surface area of the active material is 30m2g-1(ii) a At a current density of 200mA g-1After 100 cycles of charge-discharge cycle, the specific discharge capacity can be kept 320mAh g-1。
The obtained ZnFe2O4the/C is a hollow framework structure, the thickness of the carbon layer is 3.9nm, the loading capacity of the carbon is 8.8 percent, the conversion rate of the carbon is 52.8 percent, and ZnFe2O4The average grain size of the/C crystal grains is 12nm, the macropore size is 410nm, the mesopore size is 29nm, ZnFe2O4The specific surface area of the active electrode material/C is 28m2g-1(ii) a At a current density of 1A g-1After 400 cycles of charge and discharge, the specific discharge capacity can keep 698mAhg-1At a current density of 200mAg-1After 100 cycles of charge-discharge cycle, the specific discharge capacity can be kept to 950mAh g-1。
Comparative example 1-1, polyacrylic acid used in step B of examples 1-3 was eliminated, and the remaining equivalents were the same as in examples 1-3.
The obtained ZnFe2O4Particle packing of 200nm, non-porous structure, ZnFe2O4Active materialThe specific surface area is 13m2g-1(ii) a At a current density of 200mAg-1After 100 cycles of charge-discharge cycle, the specific discharge capacity can be kept to be 204 mAh g-1。
The obtained ZnFe2O4Particle stacking with 350nm of/C, non-porous structure, 4.2nm of carbon layer thickness, 9.1% of carbon loading, 54.6% of carbon conversion rate and ZnFe2O4The specific surface area of the/C active electrode material is 11m2g-1(ii) a At a current density of 200mAg-1After 100 cycles of charge-discharge cycle, the discharge specific capacitance can keep 310mAh g-1。
Comparative examples 1-2, the polyacrylic acid used in step B of examples 1-3 was changed to polyethylene oxide (PEO), and the remaining equivalents were the same as in examples 1-3.
In the experimental process, the system can not be gelatinized to form a block, after aging for 24 hours, flocculent precipitate is formed, and hierarchical porous ZnFe can not be prepared2O4A material.
Comparative examples 1-3, the amount of polyacrylic acid used in step B of examples 1-3 was changed to 24g, i.e., the mass ratio of deionized water to polyacrylic acid was 0.05: 1, the remainder being identical to examples 1 to 3.
The obtained ZnFe2O4Particle packing of 400nm, pore-free structure, ZnFe2O4The specific surface area of the active material is 12m2g-1(ii) a At a current density of 200mAg-1After 100 cycles of charge-discharge cycle, the discharge specific capacitance can retain 117 mAh g-1。
The obtained ZnFe2O4Particle stacking with/C of 550nm, non-porous structure, carbon layer thickness of 4.9nm, carbon loading of 9.9%, carbon conversion of 59.4%, ZnFe2O4The specific surface area of the/C active electrode material is 9m2g-1(ii) a At a current density of 200mAg-1After 100 cycles of charge-discharge cycle, the specific discharge capacity can be kept to 345mAh g-1。
Comparative example 2 the amount of dopamine used in step I of examples 1-3 was changed to 50mg, and the remaining amounts were the same as in examples 1-3.
The obtained ZnFe2O4Is of hollow skeleton structure, ZnFe2O4The average size of the crystal grains is 10nm, the size of macropores is 400nm, the size of mesopores is 29nm, ZnFe2O4The specific surface area of the active material is 32m2g-1(ii) a At a current density of 200mA g-1After 100 cycles of charge and discharge, the specific discharge capacity can be kept to 291mAh g-1。
Note: ZnFe prepared in this comparative example2O4ZnFe prepared in example 1-32O4The experimental data have slight deviation, which is an error caused by factors such as experimental environment and data measurement.
The obtained ZnFe2O4the/C is a hollow framework structure, the thickness of the carbon layer is 5.3nm, the loading capacity of the carbon is 10.1 percent, the conversion rate of the carbon is 60.6 percent, and ZnFe2O4The average grain size of/C is 19nm, the macropore size is 390nm, the mesopore size is 29nm, ZnFe2O4The specific surface area of the active electrode material/C is 38m2g-1(ii) a At a current density of 1A g-1The discharge specific capacitance of the capacitor can keep 691mAhg after 400 circles of charge-discharge cycle-1. At a current density of 200mAg-1After charging and discharging circulation is carried out for 100 circles, the discharge specific capacitance can keep 890mAh g-1。
Finally, it is also noted that the above-mentioned lists merely illustrate a few specific embodiments of the invention. It is obvious that the invention is not limited to the above embodiments, but that many variations are possible. All modifications which can be derived or suggested by a person skilled in the art from the disclosure of the present invention are to be considered within the scope of the invention.

Claims (4)

1. Hierarchical porous ZnFe2O4The preparation method of the negative electrode material of the/C lithium ion battery is characterized by comprising the following steps of:
s1, mixing ZnFe2O4Is added toCarrying out ultrasonic treatment on a Tris-HCl buffer solution for 10min, and then stirring for 30min to obtain a dispersion solution;
the ZnFe2O4The mass-to-volume ratio of the buffer solution to Tris-HCl buffer solution is 5 mg: 1 ml;
s2, adding dopamine into the dispersion liquid obtained in the step S1, and magnetically stirring for 24 hours to obtain suspension;
ZnFe in the step S12O4The mass ratio of the dopamine to the dopamine is 5: 1;
s3, centrifuging the suspension obtained in the step S2 for 3-5 times, and then drying the obtained black precipitate in an oven at the temperature of 40-60 ℃ for 48 +/-2 hours to obtain a black sample;
s4, placing the black sample obtained in the step S3 in a tube furnace, heating to 150 ℃ at a heating rate of 5 ℃/min under the protection of argon, preserving heat for 60min, heating to 550 ℃, preserving heat for 180min, and finally obtaining the hierarchical porous ZnFe2O4a/C lithium ion battery cathode material;
the ZnFe2O4The preparation method of (1) comprises the following steps;
A) adding deionized water into glycerol, and magnetically stirring until the deionized water and the glycerol are uniformly mixed to obtain a solution I;
B) adding polyacrylic acid into the solution I obtained in the step A), and fully stirring until the polyacrylic acid is completely dispersed and dissolved to obtain a solution II;
C) adding a zinc source and an iron source serving as precursors into the solution II obtained in the step B), and stirring until the zinc source and the iron source are completely hydrolyzed to obtain a clear and transparent solution III;
the molar ratio of the zinc source to the iron source is 0.5: 1;
D) adding a gel accelerator into the solution III obtained in the step C), and stirring for 40-60 min to obtain sol;
E) sealing the sol obtained in the step D), and placing the sol in an oven at the temperature of 40-60 ℃ for gelling for 48 +/-2 hours to obtain block gel;
F) putting the block gel obtained in the step E) into a drying oven at 40-60 ℃ for drying for 48 +/-2 hours to obtain block xerogel;
G) putting the block xerogel obtained in the step F) into a muffle furnace, and raising the temperature at 0.5-5 ℃/minRaising the temperature to 400-700 ℃ at a temperature rate, and keeping the temperature for 100-300 min to obtain ZnFe2O4。
2. The hierarchical porous ZnFe of claim 12O4The preparation method of the negative electrode material of the/C lithium ion battery is characterized by comprising the following steps of: the zinc source in the step C) is ZnCl2Or Zn (NO)3)2·6H2O, iron source being FeCl2·4H2O or Fe (NO)3)2·6H2O。
3. The hierarchical porous ZnFe of claim 22O4The preparation method of the negative electrode material of the/C lithium ion battery is characterized by comprising the following steps of: the gel accelerator used in step D) is propylene oxide or formamide.
4. The hierarchical porous ZnFe2O4/C lithium ion battery negative electrode material prepared by the method of any one of claims 1 to 3.
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