CN110395771B - Hexagonal prism-shaped cobaltosic oxide precursor and preparation method thereof, hexagonal prism-shaped cobaltosic oxide and application thereof - Google Patents
Hexagonal prism-shaped cobaltosic oxide precursor and preparation method thereof, hexagonal prism-shaped cobaltosic oxide and application thereof Download PDFInfo
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Abstract
The preparation method of the hexagonal prism-shaped cobaltosic oxide precursor comprises the steps of putting soluble cobalt salt, a plasticizer and a precipitator into water for dissolving and carrying out hydrothermal reaction, and carrying out solid-liquid separation after the reaction is finished to prepare the hexagonal prism-shaped cobaltosic oxide precursor; wherein the mol ratio of the soluble cobalt salt to the plasticizer to the precipitator is (1-5) to (3-7) to (3-9). The preparation method is simple, the prepared cobalt hydroxide is hexagonal prism-shaped by controlling the molar ratio of reactants, and the hexagonal prism-shaped cobaltosic oxide is obtained by calcining the cobalt hydroxide as a precursor. It can also be widely used in lithium ion batteries.
Description
Technical Field
The invention relates to the field of electrode materials, in particular to a hexagonal prism-shaped cobaltosic oxide precursor and a preparation method thereof, and hexagonal prism-shaped cobaltosic oxide and application thereof.
Background
Lithium Ion Batteries (LIBs) have been recognized as the most important energy storage systems in portable electronic products and automobiles. With the increasing demand for miniaturization of electrochemical energy storage devices, the development of high energy density LIBs has become an urgent task. The performance of lithium ion batteries depends to a large extent on the intrinsic properties of the electrode material. At present, the traditional carbonaceous electrode is close to the theoretical capacity limit (372mAh/g) and the development space is limited. Over the last decade, Transition Metal Oxides (TMOs), such as Fe2O3、Fe3O4、CoO、Co3O4、NiO、MnO2And the like, which are receiving wide attention due to high theoretical specific capacity, abundant reserves and high tap density. Wherein, Co3O4Is one of the most promising cathode materials, has the theoretical specific capacity of 890mAh/g, high corrosion resistance and good chemical stability.
However, Co3O4The inherent problems of which have hindered their use. One is that substantial volume changes result in severe pulverization of the electrode during lithiation/delithiation. On the other hand, Co3O4Has inherently low electron conductivity, resulting in lower rate performance. The existence of these problems directly leads to Co3O4Deterioration of reversible capacity and cycle life. Increasing Co3O4The most intuitive and common strategy for electrochemical performance of electrodes is to fabricate nanostructures. Based on these, various Co3O4Nanostructures, such as nanospheres, nanorods, nanotubes, nanowires, nanosheets, nanocubes, were successfully synthesized. These nanostructures have been shown to be effective in shortening the diffusion distance of lithium ions and mitigating severe volume changes during lithiation/delithiation. Furthermore, due to their large specific surface area, it will also provide more redox active sites and increase the surface pseudocapacitance effect, which helps to increase Co3O4The rate capability of (2). However, these nanomaterials also suffer from disadvantages such as loss of particle contact during charge/discharge, and conductive network breakdown due to agglomeration effects. Furthermore, Co3O4The nanostructures of (a) directly result in a severe loss in volumetric energy density for electrochemical energy storage applications.
In view of this, the present application is specifically made.
Disclosure of Invention
The object of the present invention includes, for example, providing a method for preparing a hexagonal prism-shaped cobaltosic oxide precursor, which is simple and economical by obtaining a specific hexagonal prism-shaped cobaltosic oxide precursor through a one-pot method.
An object of the present invention is to provide a hexagonal prism-shaped cobaltosic oxide precursor, for example, which can be used as a precursor for preparing cobaltosic oxide to obtain specific hexagonal prism-shaped cobaltosic oxide.
It is also an object of the present invention to provide, for example, a hexagonal prism-shaped cobaltosic oxide which has a higher pseudocapacitance effect and significantly increases the reaction kinetics thereof.
The invention also aims to provide the application of the hexagonal prism-shaped cobaltosic oxide in the preparation of the lithium ion battery.
Embodiments of the invention may be implemented as follows:
in a first aspect, an embodiment of the present invention provides a method for preparing a hexagonal prism-shaped cobaltosic oxide precursor, including: dissolving soluble cobalt salt, a plasticizer and a precipitator in water, carrying out hydrothermal reaction, and carrying out solid-liquid separation after the reaction is finished to prepare a hexagonal prism-shaped cobaltosic oxide precursor;
wherein the mol ratio of the soluble cobalt salt to the plasticizer to the precipitator is (1-5) to (3-7) to (3-9);
preferably, the particle size of the hexagonal prism-shaped cobalt hydroxide is 2-4 μm;
preferably, the soluble cobalt salt is a nitrate-containing cobalt salt, preferably cobalt nitrate hexahydrate;
preferably, the plasticizer contains F ions and NH at the same time4 +Ionic compounds, preferably ammonium fluoride;
preferably, the precipitate is a compound containing ammonium ions, preferably urea.
Alternatively, in other embodiments herein, the temperature of the hydrothermal reaction is 50 ℃ to 300 ℃; the reaction time is 4-8 h.
Optionally, in other embodiments of the present application, the cobalt nitrate hexahydrate is placed in water, ultrasonically dispersed, and then the ammonium fluoride and the urea are added;
preferably, the frequency of ultrasonic dispersion is 50-300 Hz;
preferably, the time for ultrasonic dispersion is 5-60 min.
In a second aspect, an embodiment of the present invention further provides a hexagonal prism-shaped cobaltosic oxide precursor, which is prepared by using the preparation method of the hexagonal prism-shaped cobaltosic oxide precursor.
In a third aspect, an embodiment of the present invention further provides a hexagonal prism-shaped cobaltosic oxide, which is prepared by calcining a hexagonal prism-shaped cobaltosic oxide precursor or a hexagonal prism-shaped cobaltosic oxide precursor prepared by the above method for preparing a hexagonal prism-shaped cobaltosic oxide precursor;
preferably, the calcining temperature is 100-800 ℃, and the calcining time is 0.5-5 h.
Alternatively, in another embodiment of the present application, the above-mentioned hexagonal prism-shaped cobaltosic oxide has a surface ratio of trivalent cobalt to divalent cobalt by mass of 1.41 to 2.11, preferably 1.58 to 1.94, and more preferably 1.76.
Optionally, in other embodiments of the present application, the hexagonal prism-shaped cobaltosic oxide has a micro-nano hierarchical structure.
Alternatively, in other embodiments of the present application, the hexagonal prism-shaped cobaltosic oxide has a hexagonal prism-shaped microstructure, and the particle size of the hexagonal prism-shaped microstructure is 2 to 4 μm;
preferably, the hexagonal prism-shaped micro-structure is distributed with nano-pores on the top surface and/or the bottom surface;
preferably, the size of the nanopore is 30-100 nm.
Optionally, in other embodiments of the present application, there are nano-spherical protrusions distributed on the side surface of the hexagonal prism-like microstructure;
preferably, the size of the nano-spherical protrusions is 50-200 nm.
In a fourth aspect, the embodiment of the present invention further provides an application of hexagonal prism-shaped cobaltosic oxide in the preparation of a lithium ion battery.
The beneficial effects of the embodiment of the invention include, for example: the preparation method of the hexagonal prism-shaped cobaltosic oxide precursor is simple, the molar ratio of the soluble cobalt salt, the plasticizer and the precipitator is controlled, the hexagonal prism-shaped cobaltosic oxide precursor can be obtained, the hexagonal prism-shaped cobaltosic oxide precursor is used as the precursor and is obtained by calcining, the rate capability and the long cycle performance of the hexagonal prism-shaped cobaltosic oxide precursor are obviously improved compared with the existing commercial cobaltosic oxide, and more importantly, the hexagonal prism-shaped cobaltosic oxide precursor has a higher pseudo-capacitance effect and the reaction kinetics of the hexagonal prism-shaped cobaltosic oxide precursor are obviously improved. The hexagonal prism-shaped cobaltosic oxide can be widely used in lithium ion batteries with high energy density, and has potential good economic benefit.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
Fig. 1 is an SEM image of a hexagonal prism-shaped cobaltosic oxide precursor provided in example 1 of the present application;
FIG. 2 is a schematic representation of the top surface and surface of hexagonal prism-shaped cobaltosic oxide provided in example 6 of the present application;
fig. 3 is an XRD pattern of hexagonal prism-shaped cobaltosic oxide provided in example 6 of the present application;
FIG. 4 is an SEM image of hexagonal prism-shaped cobaltosic oxide provided in example 6 of the present application;
FIG. 5 is a TEM image of hexagonal prism-like tricobalt tetroxide provided in example 6 of the present application;
FIG. 6 is a graph of rate capability of hexagonal prism-shaped cobaltosic oxide provided in example 13 of the present application;
FIG. 7 is a graph of the cycle performance of hexagonal prism-shaped cobaltosic oxide provided in example 13 of the present application;
FIG. 8 is a graph showing the diffusion coefficient of hexagonal prism-shaped cobaltosic oxide provided in example 13 of the present application;
FIG. 9 is an SEM image of the agglomerated random cobalt fluorohydroxide provided in comparative example 1 of the present application;
FIG. 10 is an SEM image of fine particulate cobalt fluorohydroxide that failed to nucleate growth provided by comparative example 2 of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The embodiment of the invention provides a hexagonal prism-shaped cobaltosic oxide precursor and a preparation method thereof, and hexagonal prism-shaped cobaltosic oxide and application thereof, wherein the hexagonal prism-shaped cobaltosic oxide precursor is used as a precursor for preparing the hexagonal prism-shaped cobaltosic oxide, and the hexagonal prism-shaped cobaltosic oxide precursor and the preparation method of the hexagonal prism-shaped cobaltosic oxide are explained in detail in the application.
In one aspect, the present application provides a hexagonal prism-shaped cobaltosic oxide precursor, and a preparation method thereof, including:
dissolving soluble cobalt salt, a plasticizer and a precipitator in water and carrying out hydrothermal reaction. After the reaction is finished, carrying out solid-liquid separation to obtain the hexagonal prism cobaltosic oxide precursor. Specifically, at room temperature, firstly, dissolving soluble cobalt salt in water, obtaining pink liquid after the soluble cobalt salt is uniformly dispersed, then adding a plasticizer and a precipitator, and continuously dissolving, wherein the solution is pink transparent. Transferring the uniformly mixed liquid to hydrothermal equipment, such as a reaction kettle adopted in the application, putting the liquid into an oven, carrying out hydrothermal reaction for 4-8h at 50-300 ℃, taking out and cooling to room temperature. And performing solid-liquid separation to obtain pink powder, and preparing a hexagonal prism cobaltosic oxide precursor.
In the embodiment, the molar ratio of the soluble cobalt salt to the plasticizer to the precipitator is (1-5) to (3-7) to (3-9), and the soluble cobalt salt is selected from at least one of cobalt salts containing nitrate radicals, preferably cobalt nitrate hexahydrate; the plasticizer is selected from the group consisting of F ions and NH4 +At least one of ionic compounds, preferably ammonium fluoride; the precipitate is at least one selected from compounds containing ammonium ions, preferably urea. Mixing soluble cobalt salt, a plasticizer and a precipitator for hydrothermal reaction, and carrying out solid-liquid separation on the generated precipitate to obtain the product, namely the hexagonal prism-shaped cobaltosic oxide precursorThe grain diameter of the prism-shaped cobaltosic oxide precursor is 2-4 mu m.
In the present application, by controlling the molar ratio of the reactants, a hexagonal prism-shaped cobaltosic oxide precursor having a specific shape (hexagonal prism shape) can be generated during the hydrothermal reaction (specifically, in the present embodiment, the hexagonal prism-shaped cobaltosic oxide precursor is cobalt hydroxide fluoride having a chemical formula of co (oh) F), the molar ratio of the soluble cobalt salt, the plasticizer and the precipitant can affect the process of the mixing reaction of the soluble cobalt salt, the plasticizer and the precipitant, and in this embodiment, selecting the mol ratio of the soluble cobalt salt to the plasticizer to the precipitator as (1-5): (3-7): (3-9), the molar ratio of the reactants is different from the reported reactant ratio, the prepared Co (OH) F is mainly nano-wires or irregular particles reported in the literature, and the cobaltosic oxide with the corresponding morphology formed after further calcination treatment has no special characteristics in the aspect of lithium storage. However, when the molar ratio is too large, the Co (OH) F can generate serious agglomeration effect in the nucleation process to form irregular granular products, and when the molar ratio of the reactants is too small, the Co (OH) F can not grow further after the nucleation, so that micron-sized single-crystal hexagonal prism-shaped Co (OH) F can not be obtained. The appropriate molar ratio is therefore critical for the formation of hexagonal prism-like Co (OH) F.
In addition, the temperature and the time of the hydrothermal reaction can ensure that the cobalt nitrate hexahydrate, the ammonium fluoride and the urea react completely. The water in this application includes, but is not limited to, ultrapure water, pure water, distilled water, deionized water, etc., and preferably, the ultrapure water is selected for dissolving the cobalt nitrate hexahydrate, ammonium fluoride, and urea in this embodiment. In this embodiment, ultrasonic dispersion is used to assist the cobalt nitrate hexahydrate in dissolving, so that the cobalt nitrate hexahydrate is dispersed more uniformly. Specifically, the frequency of ultrasonic dispersion is 50-300 Hz; the ultrasonic dispersion time is 5-60 min. It is understood that in other embodiments of the present application, the mixing may also be performed by other means, such as stirring, shaking, etc.
The hexagonal prism-shaped cobaltosic oxide precursor obtained by the above preparation method has a specific hexagonal prism shape, and can be used as a precursor for preparing hexagonal prism-shaped cobaltosic oxide.
In a second aspect, the application also provides hexagonal prism-shaped cobaltosic oxide, which is prepared by calcining the hexagonal prism-shaped cobaltosic oxide precursor at the temperature of 100-800 ℃ for 0.5-5 h.
The hexagonal prism-shaped cobaltosic oxide is prepared by adopting the specific precursor, and the mass ratio of the trivalent cobalt to the divalent cobalt on the surface of the obtained hexagonal prism-shaped cobaltosic oxide is 1.41-2.11, preferably 1.58-1.94, and more preferably 1.76. In the prior art, the content ratio of trivalent cobalt to divalent cobalt in conventional cobaltosic oxide is about 1, and it can be seen that the content ratio of trivalent cobalt to divalent cobalt in the present application is significantly higher than that in the prior art, which shows that the hexagonal prism-shaped cobaltosic oxide provided by the present application is a material rich in trivalent cobalt, and the increase of the content of high valence cobalt is beneficial to increase the specific capacity of cobaltosic oxide in a lithium battery, and the increase of high valence cobalt also causes the increase of oxygen vacancies inside the cobaltosic oxide material, and the increase of oxygen vacancies can significantly increase the conductivity of the material, thereby improving the first-turn coulombic efficiency of cobaltosic oxide. Compared with the existing commercial cobaltosic oxide, the rate capability and the long cycle capability are obviously improved, and more importantly, the cobaltosic oxide has higher pseudo-capacitance effect and obviously increases the reaction kinetics.
The hexagonal-prism-shaped cobaltosic oxide in the embodiment has a micro-nano hierarchical structure, and is decomposed into porous cobaltosic oxide through hexagonal-prism-shaped co (oh) F during calcination, and the hexagonal-prism-shaped structure is maintained. Specifically, the hexagonal prism-shaped cobaltosic oxide has a hexagonal prism-shaped microstructure, the grain size of the hexagonal prism-shaped microstructure is 2-4 μm, and preferably, nanopores are distributed on the top surface and/or the bottom surface of the hexagonal prism-shaped microstructure; preferably, the size of the nanopores is 30-100 nm. Nano spherical bulges are distributed on the side surface of the hexagonal prism-shaped micro structure; preferably, the size of the nano-spherical protrusions is 50-200 nm.
In the present application, the porous roughness structure formed by calcination greatly increases the hexagonal prism shapeThe specific surface area of the cobaltosic oxide can provide more redox active sites and increase the surface pseudocapacitance effect, thereby improving the Co3O4The rate capability of (2).
The hexagonal prism-shaped cobaltosic oxide provided by the application can be widely applied to the lithium ion battery with high energy density, and has potential good economic benefits.
The preparation method of the hexagonal-prism-shaped cobaltosic oxide precursor is simple, and by controlling the molar ratio of cobalt nitrate hexahydrate, ammonium fluoride and urea, wherein the ammonium fluoride is used as a plasticizer, and the urea is used as a precipitator, the prepared cobalt fluoride hydroxide is hexagonal-prism-shaped, and the prepared cobalt fluoride hydroxide is calcined as a precursor to obtain the hexagonal-prism-shaped cobaltosic oxide. The hexagonal prism-shaped cobaltosic oxide can be widely used in lithium ion batteries with high energy density, and has potential good economic benefit.
Next, the hexagonal prism-shaped cobaltosic oxide precursor, the preparation method thereof, the hexagonal prism-shaped cobaltosic oxide, and the application thereof will be specifically described with reference to specific examples.
Example 1
The embodiment provides a preparation method of a hexagonal prism-shaped cobaltosic oxide precursor, which comprises the following steps:
the cobalt nitrate hexahydrate, the ammonium fluoride and the urea are proportioned according to the molar ratio of 1:3: 3. At room temperature, 0.293g of cobalt nitrate hexahydrate (Co (NO)3)2·6H2O) was placed in 40ml of ultrapure water, dispersed for 10min at an ultrasonic frequency of 100Hz, and dissolved to give a pink liquid. 0.093g ammonium fluoride (NH4F) and 0.15g urea (CO (NH)2)2) The solution is dissolved by adding the solution, and the solution is pink transparent. And transferring the mixed solution into a hydrothermal reaction kettle, putting the hydrothermal reaction kettle into an oven, carrying out hydrothermal reaction for 6 hours at the temperature of 80 ℃, taking out the hydrothermal reaction kettle, and cooling to room temperature. Filtering to obtain pink powderAnd finally, obtaining the hexagonal prism cobaltosic oxide precursor. The SEM is shown in FIG. 1. As can be seen from FIG. 1, the size of the prepared hexagonal-prism-shaped cobalt hydroxide is about 2-4 μm, the precursor has relatively uniform morphology and particle size, the side surfaces of the hexagonal-prism-shaped cobalt hydroxide have a hierarchical nano-lamellar structure, and the top surface of the hexagonal-prism-shaped cobalt hydroxide has a smooth pore-free structure.
Example 2
The embodiment provides a preparation method of a hexagonal prism-shaped cobaltosic oxide precursor, which comprises the following steps:
the cobalt nitrate hexahydrate, the ammonium fluoride and the urea are mixed according to the molar ratio of 5:7: 9. Cobalt nitrate hexahydrate (Co (NO) at room temperature3)2·6H2O) was placed in 50ml of ultrapure water, dispersed for 5min at an ultrasonic frequency of 200 and dissolved to give a pink liquid. Then ammonium fluoride (NH4F) and urea (CO (NH)2)2) The solution is dissolved by adding the solution, and the solution is pink transparent. And transferring the mixed solution into a hydrothermal reaction kettle, putting the hydrothermal reaction kettle into an oven, carrying out hydrothermal reaction for 8 hours at the temperature of 200 ℃, taking out the hydrothermal reaction kettle, and cooling to room temperature. And carrying out suction filtration to obtain pink powder, namely the hexagonal prism-shaped cobaltosic oxide precursor. The size of the prepared hexagonal prism-shaped cobalt hydroxide is about 2-4 mu m, the precursor has relatively uniform appearance and particle size, the side surface of the hexagonal prism-shaped cobalt hydroxide has a layered nano-sheet structure, and the top surface of the hexagonal prism-shaped cobalt hydroxide is smooth and has no pore structure.
Examples 3 to 5
This example provides a hexagonal prism-shaped cobaltosic oxide precursor, which is prepared substantially in the same manner as in example 1, except that:
in example 3, the molar ratio of cobalt nitrate hexahydrate, ammonium fluoride and urea was 2:3: 6.
in example 4, the molar ratio of cobalt nitrate hexahydrate, ammonium fluoride and urea was 3:6: 8.
in example 5, the molar ratio of cobalt nitrate hexahydrate, ammonium fluoride and urea was 4:5: 7.
example 6
The embodiment provides hexagonal prism-shaped cobaltosic oxide, which is obtained by placing the hexagonal prism-shaped cobaltosic oxide precursor prepared in the embodiment 1 in a muffle furnace at room temperature, heating to 400 ℃, and calcining for 2 hours to obtain a black product, namely the hexagonal prism-shaped cobaltosic oxide cathode material. The average particle size of the hexagonal prism-shaped cobaltosic oxide in this example was 4 μm, the hexagonal prism-shaped cobaltosic oxide had a hexagonal prism-shaped microstructure, nanopores having a size of 5 to 20nm were distributed on the top surface of the hexagonal prism-shaped microstructure, and nanosphere-shaped protrusions having a size of 5 to 10nm were distributed on the side surface of the hexagonal prism-shaped microstructure. (see FIG. 2). The XRD, SEM and TEM images are shown in FIGS. 3, 4 and 5, respectively.
As can be seen from fig. 3, the X-ray diffraction peaks of the hexagonal prism-shaped trivalent cobalt-rich hexagonal cobaltosic oxide completely correspond to those of the standard cards 43-1003, indicating that the hexagonal prism-shaped cobaltosic oxide has a pure spinel structure.
As can be seen from fig. 4, the particle size of the hexagonal prism-shaped trivalent cobalt-rich hexagonal cobaltosic oxide is about 4 μm, the morphology of hexagonal prism-shaped co (oh) F is maintained by the particle structure, and nanopores with the size of 5-20nm are distributed on the top surface of the hexagonal prism-shaped microstructure, and nanosphere-shaped protrusions with the size of 5-10nm are distributed on the side surface of the hexagonal prism-shaped microstructure.
As can be seen from fig. 5, the hexagonal prism-shaped trivalent cobalt-rich hexagonal cobaltosic oxide has convex particles at the edges, and further, the cobaltosic oxide has six solid sides without pores while having a porous structure from top to bottom in the middle, which is consistent with the results of SEM.
Examples 7 to 10
In examples 7 to 10, the hexagonal prism-shaped cobaltosic oxide precursors prepared in examples 2 to 5 were used as precursors, and were placed in muffle furnaces, respectively, and were calcined at 600 ℃ for 3 hours, and the black product was the hexagonal prism-shaped cobaltosic oxide negative electrode material.
Example 11
The embodiment provides hexagonal prism-shaped cobaltosic oxide, which is obtained by placing the hexagonal prism-shaped cobaltosic oxide precursor prepared in the embodiment 1 in a muffle furnace at room temperature, heating to 800 ℃, and calcining for 1h to obtain a black product, namely the hexagonal prism-shaped cobaltosic oxide cathode material.
Example 12
The embodiment provides hexagonal prism-shaped cobaltosic oxide, which is obtained by placing the hexagonal prism-shaped cobaltosic oxide precursor prepared in the embodiment 1 in a muffle furnace at room temperature, heating to 200 ℃, and calcining for 5 hours to obtain a black product, namely the hexagonal prism-shaped cobaltosic oxide cathode material.
Example 13
The performance of the hexagonal prism-shaped cobaltosic oxide is shown as follows:
punching a round piece with the diameter of 15mm from the prepared cobaltosic oxide negative electrode material to be used as a negative electrode plate, using a lithium foil as a positive electrode plate, using a polypropylene microporous membrane (Cellgard 2300) as a diaphragm, and selecting an electrolyte (LiPF in the electrolyte)6The concentration of the carbon dioxide is 1mol/L, the rest is ethylene carbonate and diethyl carbonate with the volume ratio of 1: 1), a CR2025 button type analog battery is assembled in a glove box filled with argon, a battery packaging machine is used for sealing, a half battery is obtained, a constant current is used for carrying out charge-discharge test, and the charge-discharge voltage is between 0.01 and 3.0V. The rate capability and cycling capability are shown in fig. 6 and 7, and the diffusion coefficient calculation is shown in fig. 8.
As can be seen from FIG. 6, the current density was programmed to be 50mA g-1Rise to 200mA g-1，500mA g-1,1000mA g-1And finally to 50mA g-1The specific capacities of hexagonal prism-shaped trivalent cobalt-rich hexagonal cobaltosic oxide are 1100, 1090,910,630 and 1140mAh g respectively-1And when the current density is recovered to 50mA g-1The specific capacity of the hexagonal prism-shaped trivalent cobalt-rich hexagonal cobaltosic oxide tends to increase, and the result shows that the hexagonal prism-shaped trivalent cobalt-rich hexagonal cobaltosic oxide has excellent rate capability.
As can be seen from FIG. 7, when the voltage window is in the range of 0.01-3.0V, the current density is 500mA g-1Long-time circulation test is carried out, and the specific capacity of the hexagonal prism-shaped trivalent cobalt-rich hexagonal cobaltosic oxide is kept at 900mAh g after 500 cycles of circulation-1Nearby, the hexagonal prism-shaped trivalent cobalt-rich hexagonal cobaltosic oxide is proved to have excellent electrochemical stability and high specific capacity.
In fig. 8, CHP is hexagonal prism-shaped cobaltosic oxide of the present application, CCN is a reference sample (cobaltosic oxide nanowire), CNW is (cobaltosic oxide micron commercial particle), and as can be seen from fig. 7, in the voltage interval of 0.01-3V, except for 1.5V, which has similar lithium ion diffusion coefficients, CHP exhibits lithium ion diffusion coefficients much higher than those of CCN and CNW in the intervals of 0.01-1.5V and 1.5V-3V, indicating that CHP possesses contact kinetics.
Comparative examples 1 to 2
Comparative examples 1 and 2 provide a hexagonal prism-shaped cobaltosic oxide precursor, which is prepared substantially in the same manner as in example 1, except that:
in comparative example 1, the molar ratio of cobalt nitrate hexahydrate, ammonium fluoride and urea was 1: 8: 10.
in comparative example 2, the molar ratio of cobalt nitrate hexahydrate, ammonium fluoride and urea was 1: 2: 2.
referring to FIG. 9, when the molar ratio of the reactants is too large, the Co (OH) F will cause serious agglomeration effect during the nucleation process, and form irregular granular products. Referring to fig. 10, when the molar ratio of the reactants is too small, co (oh) F cannot grow further after nucleation, and thus micron-sized single-crystal hexagonal-prism-shaped co (oh) F cannot be obtained.
In summary, the preparation method of the hexagonal-prism-shaped cobaltosic oxide precursor provided by the application is simple, the hexagonal-prism-shaped cobaltosic oxide precursor can be prepared by controlling the molar ratio of the soluble cobalt salt, the plasticizer and the precipitator, and the hexagonal-prism-shaped cobaltosic oxide precursor is obtained by calcining the precursor. The hexagonal prism-shaped cobaltosic oxide can be widely used in lithium ion batteries with high energy density, and has potential good economic benefit.
The above description is only for the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (21)
1. A preparation method of a hexagonal prism-shaped cobaltosic oxide precursor is characterized by comprising the following steps: dissolving soluble cobalt salt, a plasticizer and a precipitator in water, carrying out hydrothermal reaction, and carrying out solid-liquid separation after the reaction is finished to prepare a hexagonal prism-shaped cobaltosic oxide precursor;
wherein the molar ratio of the soluble cobalt salt, the plasticizer and the precipitant is 1:3:3, 5:7:9, 2:3:6, 3:6:8 or 4:5: 7; the plasticizer is ammonium fluoride; the precipitant is urea.
2. The method according to claim 1, wherein the particle size of the hexagonal prism-shaped cobaltosic oxide precursor is 2 to 4 μm.
3. The method for producing a hexagonal prism-shaped cobaltosic oxide precursor according to claim 1, wherein the soluble cobalt salt is a nitrate-containing cobalt salt.
4. The method of preparing a hexagonal-prism-shaped cobaltosic oxide precursor according to claim 1, wherein the soluble cobalt salt is cobalt nitrate hexahydrate.
5. The method for preparing a hexagonal prism-shaped cobaltosic oxide precursor according to claim 1, wherein the temperature of the hydrothermal reaction is 50 ℃ to 300 ℃; the reaction time is 4-8 h.
6. The method for preparing a hexagonal prism-shaped cobaltosic oxide precursor according to claim 1, wherein the soluble cobalt salt is placed in water, ultrasonically dispersed, and then the plasticizer and the precipitant are added.
7. The method for preparing a hexagonal prism-shaped cobaltosic oxide precursor according to claim 6, wherein the frequency of ultrasonic dispersion is 50 to 300 Hz.
8. The method for preparing a hexagonal prism-shaped cobaltosic oxide precursor according to claim 6, wherein the ultrasonic dispersion time is 5-60 min.
9. A hexagonal prism-shaped cobaltosic oxide precursor, characterized by being prepared by the method for preparing a hexagonal prism-shaped cobaltosic oxide precursor according to any one of claims 1 to 8.
10. A hexagonal prism-shaped cobaltosic oxide precursor prepared by the method for preparing a hexagonal prism-shaped cobaltosic oxide precursor according to claim 1 or obtained by calcining a hexagonal prism-shaped cobaltosic oxide precursor according to claim 9.
11. The hexagonal prism-shaped cobaltosic oxide according to claim 10, wherein the calcination temperature is 100 ℃ to 800 ℃ and the calcination time is 0.5 to 5 hours.
12. The hexagonal-prism-shaped cobaltosic oxide according to claim 10, wherein the hexagonal-prism-shaped cobaltosic oxide has a surface ratio of trivalent cobalt to divalent cobalt by mass of 1.41 to 2.11.
13. The hexagonal-prism-shaped cobaltosic oxide according to claim 10, wherein the hexagonal-prism-shaped cobaltosic oxide has a surface ratio of trivalent cobalt to divalent cobalt by mass of 1.58 to 1.94.
14. The hexagonal-prism-shaped cobaltosic oxide according to claim 10, wherein the hexagonal-prism-shaped cobaltosic oxide has a surface ratio of trivalent cobalt to divalent cobalt by mass of 1.76.
15. The hexagonal-prism-shaped cobaltosic oxide according to claim 10, wherein the hexagonal-prism-shaped cobaltosic oxide has a micro-nano hierarchical structure.
16. The hexagonal-prism-shaped cobaltosic oxide according to claim 10, wherein the hexagonal-prism-shaped cobaltosic oxide has a hexagonal-prism-shaped microstructure, and the particle size of the hexagonal-prism-shaped microstructure is 2-4 μ ι η.
17. The hexagonal-prism-shaped cobaltosic oxide according to claim 16, wherein the hexagonal-prism-shaped microstructures have nanopores distributed on top and/or bottom surfaces thereof.
18. The hexagonal-prism-shaped cobaltosic oxide according to claim 17, wherein the size of the nano-pores is 30-100 nm.
19. The hexagonal-prism-shaped cobaltosic oxide according to claim 16, wherein nano-spherical protrusions are distributed on the side surfaces of the hexagonal-prism-shaped micro-structures.
20. The hexagonal-prism-shaped cobaltosic oxide according to claim 19, wherein the size of the nano-spherical protrusions is 50 to 200 nm.
21. Use of hexagonal prism-shaped cobaltosic oxide according to any one of claims 10 to 20 for the preparation of a lithium ion battery.
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