CN109904435B - Preparation method of composite electrode material and composite electrode material - Google Patents
Preparation method of composite electrode material and composite electrode material Download PDFInfo
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Abstract
The invention discloses a preparation method of a composite electrode material and the composite electrode material. The preparation method of the composite electrode material comprises the following steps: preparing a LLOs @ LATP composite material; adding CNTs into a mixed acid solution, heating, washing the CNTs with water to be neutral, and obtaining CNTs subjected to acid treatment; dispersing the CNTs subjected to acid treatment in an alcohol solvent, adding the LLOs @ LATP composite material, then carrying out ultrasonic stirring, washing a product with ethanol, and drying to obtain the LLOs @ LATP @ CNTs composite material. According to the invention, the composite electrode material with a double-coating structure is prepared by coating the CNTs on the LLOs @ LATP composite material, so that the electronic conductivity and the ionic conductivity of the whole electrode material can be improved simultaneously, the problems of material capacity attenuation and voltage reduction are further relieved, and the effect of improving the electrochemical performance of the electrode material in a synergistic manner is achieved.
Description
Technical Field
The invention relates to the field of electrode materials, in particular to a preparation method of a composite electrode material and the composite electrode material.
Background
Along with the increasing demand of people for energy and the continuous deepening of understanding of the importance of sustainable development of society and economy, the lithium ion battery which is characterized by environmental protection, high efficiency and high energy is more and more emphasized by people. The application of large and medium electric tools, energy storage power stations, electric vehicles, smart power grids and the like puts higher requirements on the aspects of energy density, safety, power density, cycle life, price, environmental friendliness and the like of lithium ion batteries. Among them, the performance of the positive electrode material of the lithium ion battery has become a decisive factor for influencing the energy density of the whole battery. Therefore, developing a lithium ion battery cathode material with high capacity, long cycle life and good rate capability becomes one of the current research hotspots.
At present, LiCoO is mainly used as the main commercialized lithium ion battery anode material2，LiFePO4，LiMnxNiyCo1-x-yO2 (0<x, y<0.5), and the like. LiCoO2Due to Co3+The cobalt is a scarce resource, the preparation cost is high, and the cobalt can only be applied to small batteries; LiFePO4Due to intrinsic low electronic and ionic conductivity and pure-phase LiFePO4Difficult to synthesize and LiFePO4The capacity and the tap density are difficult to be considered; LiMnxNiyCo1-x-yO2Integrated LiCoO2、LiMnO2And LNiO2The advantages of (1). However, the expansion of the application field of the lithium ion battery especially in the aspect of pure electric vehicles requires high specific energy (300 Wh kg)-1And above), there is a strong need for high specific energy materials, particularly high specific capacity lithium ion battery positive electrode materials.
Near phase, one class is based on Li2MnO3High specific capacity (200-300 mAh g)-1) Positive electrode material zLi2MnO3·(1-z)LiMO2 (0<z<1, M=Mn0.5Ni0.5, MnxNiyCo1-x-y, 0<x, y<0.5) (lithium-rich layered cathode material), has attracted extensive attention and has become a research hotspot, becoming one of the most promising materials to meet this requirement. However, the lithium-rich layered cathode material has several important problems to be solved urgently, mainly in Li2MnO3During the activation of the components, oxygen is irreversibly released, resulting in the transformation of the layered structure of the material to the spinel phase, which in turn leads to severe discharge voltage decay, and during high voltage cycling, oxygen is releasedThe release of the carbonate electrolyte accelerates the decomposition of the carbonate electrolyte, side reactions between an electrode and the electrolyte and the like, and finally leads to the rapid reduction of the battery capacity, and the lower conductivity of the material leads to the poor rate capability, which seriously hinders the commercial application of the material.
In recent years, in order to solve the above problems, researchers have performed a lot of work, and the modification method mainly includes: doping, such as Al, Cr and the like; ② surface coatings, e.g. Al2O3、Al(OH)3、AlPO4The dissolution of metal ions is prevented, the occurrence of side reactions is inhibited, and the capacity retention rate of the positive electrode material is improved; using inorganic acid or organic weak acid to pretreat the material; compounding the lithium-rich material with the lithium-deficient carrier, so that lithium ions which are irreversibly removed during first discharge can be inserted into the lithium-deficient carrier, and the irreversible capacity is reduced; and (6) nanocrystallizing the particles to ensure that the active material is fully contacted with the electrolyte, shortening the diffusion path of lithium ions and improving the rate capability of the material.
Manthiram research group aided in past work on LiCoO2Surface modification method of positive electrode material using Al2O3、AlPO4Metallic simple substance Al, Al2O3-RuO2Mixed coating material and graphite, etc. for Li [ Li ] as lithium-rich layered positive electrode material0.2Mn0.54Ni0.13Co0.13]O2And carrying out surface coating modification. They found that the surface coating modification can improve the first discharge capacity of the material from 250 mAh g-1The left and right are improved to 280 mAh g-1About, irreversible capacity loss is reduced by 35-50 mAh g-1And the cycle performance and the coulombic efficiency of the material are improved. By comparing Al2O3、CeO2、ZrO2、SiO2、ZnO、AlPO4Isoclad material and F-The effect of doping on the performance of the anode material, they found that Al2O3The coated material has better cycle performance and passes through AlPO4The coated positive electrode material has lower first cycle irreversible capacity loss.
Coating by atomic layer deposition has also been improved in recent yearsIt is good for material performance. Von doctor national institute of physical research of Chinese academy of sciences utilizes atomic layer deposition method in Li1.2Ni0.17Mn0.56Co0.07O2Depositing a layer of Al with controllable thickness on the surface of the material2O3Layer of reversible capacity of the electrode material from 200 mAh g-1Increased to 250 mAh g-1When the thickness of the coating layer is less than 5 nm, the surface is coated with Al2O3And also to suppress polarization of the material. The surface modification improves the structural stability and the cycle performance of the material at the same time.
The surface coating is one of the most widely applied methods for improving the electrochemical performance of the lithium-rich layered cathode material at present. In recent years, the surface of the lithium-rich layered cathode material is coated and modified by adopting common metal oxide (Al)2O3、TiO2Etc.), phosphates (AlPO)4、CoPO4Etc.), carbon, through a lithium ion conductor (LiAlO)2Etc.) surface coating modification thereof is emerging. The corrosion of the electrolyte to the surface of the electrode material is reduced through surface coating, the structural stability of the material is enhanced, and meanwhile, the electronic conductivity (carbon) or the ionic conductivity (lithium ion conductor) can be improved through surface modification, so that the multiplying power performance of the electrode material is improved. However, most common metal oxides (Al)2O3、TiO2Etc.) itself has low electron conductivity and ion conductivity, and a lithium ion conductor (LiAlO)2Etc.), and the ion conductivity of a common carbon layer is low, the effects of enhancing the electron conductivity and the ion conductivity cannot be simultaneously achieved when these single materials are used as a coating layer, but the electron conductivity or the ion conductivity of the materials is inhibited, so that better electrochemical performance cannot be obtained.
Accordingly, the prior art is yet to be improved and developed.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a preparation method of a composite electrode material and the composite electrode material, and aims to solve the problem that the electronic conductivity and the ionic conductivity of the electrode material cannot be enhanced simultaneously in the existing surface coating technology, so that the electrochemical performance is not high.
A method for preparing a composite electrode material, comprising the steps of:
preparing a LLOs @ LATP composite material;
adding CNTs into a mixed acid solution, heating, washing the CNTs with water to be neutral, and obtaining CNTs subjected to acid treatment;
dispersing the CNTs subjected to acid treatment in an alcohol solvent, adding the LLOs @ LATP composite material, then carrying out ultrasonic stirring, washing a product with ethanol, and drying to obtain the LLOs @ LATP @ CNTs composite material.
The preparation method of the composite electrode material comprises the following steps:
adding lithium nitrate, aluminum nitrate, tetrabutyl titanate and ammonium dihydrogen phosphate into a citric acid aqueous solution, and stirring until the solution becomes clear to obtain a precursor sol of lithium aluminum titanium phosphate;
adding lithium-rich layered oxide into the precursor sol of the lithium aluminum titanium phosphate, evaporating the solvent to obtain a precursor LLOs @ LATP, and calcining at high temperature to obtain the LLOs @ LATP composite material.
The preparation method of the composite electrode material comprises the step of mixing the sulfuric acid and the nitric acid to obtain a mixed acid solution.
The preparation method of the composite electrode material comprises the following steps of dispersing the acid-treated CNTs in an alcohol solvent: a dispersant is added to an alcohol solvent.
The preparation method of the composite electrode material comprises the step of preparing the composite electrode material by using an alcohol solvent, wherein the alcohol solvent is one of ethanol, glycol and butanol.
The preparation method of the composite electrode material comprises the step of preparing a dispersion medium, wherein the dispersion medium is one of polyvinylpyrrolidone, sodium dodecyl benzene sulfonate, sodium dodecyl sulfate and sodium hexadecyl polyoxyethylene ether phosphate.
The preparation method of the composite electrode material is characterized in that the drying temperature is 60-90 ℃.
The preparation method of the composite electrode material is characterized in that the high-temperature calcination temperature is 500-900 ℃.
A composite electrode material, comprising: the lithium-rich layered oxide comprises a lithium-rich layered oxide, titanium aluminum lithium phosphate coated on the lithium-rich layered oxide, and a carbon nano tube coated on the titanium aluminum lithium phosphate.
The composite electrode material is characterized in that the mass percentage of the carbon nano tubes in the composite electrode material is 1% -5%.
Has the advantages that:
according to the invention, the lithium-rich layered cathode material is subjected to double-layer coating by adopting the fast ion conductor LATP with high ionic conductivity and the electronic conductor CNTs with high electronic conductivity, so that the overall conductivity of the material (both the electronic conductivity and the ionic conductivity are improved) can be improved while the structural transformation of the material and the side reaction with the electrolyte are inhibited and the oxidative decomposition of the electrolyte is slowed down, thereby further relieving the problems of material capacity attenuation and voltage reduction and synergistically improving the electrochemical performance of the material.
Drawings
FIG. 1 is an SEM photograph of four electrode materials in example 1 of the present invention.
FIG. 2 is a TEM image of four electrode materials in example 1 of the present invention.
FIG. 3 is a graph of rate capability of four electrode materials in example 1 of the present invention.
FIG. 4 is a graph of the cycling performance at 0.2C current density for four electrode materials in example 1 of the present invention.
Detailed Description
The present invention provides a method for preparing a composite electrode material and a composite electrode material, and the present invention is further described in detail below in order to make the objects, technical solutions and effects of the present invention clearer and clearer. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The meaning of the special noun and the meaning of the English abbreviation:
the LLOs @ LATP composite material is characterized in that the surface of the lithium-rich layered oxide is coated with titanium aluminum lithium phosphate. The LLOs @ LATP @ CNTs composite material is characterized in that the surface of the LLOs @ LATP composite material is coated with carbon nanotubes.
Compared with the ion insulation property of common metal oxide, the lithium ion conductor has higher ion conductivity, improves the structural stability and the thermal stability of the lithium-rich layered cathode material, inhibits the side reaction between the cathode material and the electrolyte, can avoid influencing the transmission of lithium ions after coating, even improves the diffusion rate of the lithium ions, and further improves the electrochemical performance of the cathode material. However, lithium ion conductors having low electron conductivity inhibit electron transfer. The solid electrolyte (fast ion conductor) has higher ion conductivity as a special lithium ion conductor, wherein, the glass ceramic [ Li ]1+xAlxTi2-x(PO4)3](LATP, x = 0.3-0.5) is a NASICON type structure and has an ionic conductivity of 10 at room temperature-4 S cm-1Is a good fast ion conductor; the CNTs have a special one-dimensional structure, so that the transmission of lithium ions can be accelerated to a certain extent while the CNTs have high electronic conductivity, and therefore, the electrochemical performance of the material is synergistically improved by adopting the LATP lithium ion conductor and the CNTs electronic conductor to double-coat the lithium-rich layered oxide material.
The invention provides a preparation method of a composite electrode material, which comprises the following steps:
preparing a LLOs @ LATP composite material;
adding CNTs into a mixed acid solution, heating, washing the CNTs with water to be neutral, and obtaining CNTs subjected to acid treatment;
dispersing the CNTs subjected to acid treatment in an alcohol solvent, adding the LLOs @ LATP composite material, then carrying out ultrasonic stirring, washing a product with ethanol, and drying to obtain the LLOs @ LATP @ CNTs composite material, namely the composite electrode material.
According to the invention, the composite electrode material with a double-coating structure is prepared by coating a layer of CNTs on the LLOs @ LATP composite material. The double coating of the lithium ion conductor LATP and the electronic conductor CNTs inhibits the transition of the lithium-rich layered anode material LLOs from a layered state to a spinel phase, improves the structural stability of the material, and slows down the attenuation of discharge voltage.
Meanwhile, the corrosion resistance of the coating material to acidic substances in the electrolyte is utilized, the contact area between the electrode material and the electrolyte is reduced through surface coating, the corrosion of the electrolyte to the surface of the electrode material is reduced, and the side reaction of the surface of the electrode material in the charging and discharging process is inhibited.
In addition, the CNTs have a certain degree of adsorption effect on oxygen, so that the accelerated decomposition of the carbonate electrolyte under high voltage is relieved, and the circulation stability of the material is improved.
The surface modification of the lithium ion conductor LATP and the electronic conductor CNTs respectively improves the diffusion rate of lithium ions and electrons, enhances the ionic conductivity and the electronic conductivity in the LLOs @ LATP @ CNTs composite material, improves the overall conductivity of the material, and improves the rate capability of the electrode material. The synergistic effect of the LATP and the CNTs enables the LLOs @ LATP @ CNTs composite material to have the highest capacity, the most stable cycle performance and the best rate performance.
Preferably, the present invention also provides a method for preparing LLOs, comprising the steps of:
reacting LiOH2O、Mn(CH3COO3)2•4H2O、Ni(CH3COO3)2•4H2O、Co(CH3COO3)2•4H2O、H2C2O4Adding (oxalic acid) into an ethanol aqueous solution, heating for 15-24h at the temperature of 150-200 ℃, washing the obtained product with water and ethanol, and drying at the temperature of 70-100 ℃ to prepare Li1.2Mn0.54Ni0.13Co0.13O2(LLOs) precursor powder;
subjecting the Li to1.2Mn0.54Ni0.13Co0.13O2The precursor powder is calcined at the high temperature of 500-900 ℃ to obtain LLOs。
Preferably, the lioh2O、Mn(CH3COO3)2•4H2O、Ni(CH3COO3)2•4H2O、Co(CH3COO3)2•4H2The amount ratio of O substance is 1.2:0.54:0.13:0.13, that is, the raw materials are added into the ethanol water solution according to the stoichiometric ratio.
The preparation method of the LLOs is also a liquid phase preparation method, wherein the solvent is ethanol water solution. Preferably, the mass ratio of ethanol to water in the aqueous ethanol solution is 1: 1.
Preferably, the preparation of the LLOs @ LATP composite comprises the steps of:
lithium nitrate (LiNO)3) Aluminum nitrate (Al (NO)3)3•9H2O), tetrabutyl titanate (Ti (OC)4H9)4) Ammonium dihydrogen phosphate (NH)4H2PO4) Adding to citric acid (C)6H8O7) Stirring the solution for 0.5 to 3 hours at the temperature of between 50 and 100 ℃ in the aqueous solution until the solution becomes clear to obtain a precursor sol of LATP;
adding lithium-rich layered oxide into the precursor sol of the LATP, evaporating the solvent to obtain a precursor LLOs @ LATP, and calcining at high temperature to obtain the LLOs @ LATP composite material.
Preferably, the solvent is evaporated by stirring, ball milling, ultrasound and the like, and the temperature of the evaporated solvent is controlled to be 70-110 ℃. Further, the stirring and mixing time is 3-8 h. In the process of evaporating the solvent, the method of ball milling, stirring, ultrasound and the like are adopted to realize the coating of the LLOs by the LATP.
Preferably, the step of evaporating the solvent further comprises drying to remove the residual solvent. Wherein the drying temperature is 80-150 ℃, and the drying time is 5-14 h.
Preferably, the high-temperature calcination temperature is 500-900 ℃, and the high-temperature calcination time is 3-7 h. The invention obtains the LLOs @ LATP composite material by high-temperature calcination to make the LLOs @ LATP precursor react.
Preferably, the mixed acid solution is a mixed solution of sulfuric acid and nitric acid. More preferably, the volume ratio of sulfuric acid to nitric acid in the mixed acid solution is 1: 3. The CNTs which are not treated by acid have longer length and are directly used for coating, so the effect is not good. Therefore, the CNTs are subjected to acid treatment and are cut short, more oxygen-containing groups are generated on the CNTs, and the generated oxygen-containing groups can adsorb oxygen to a certain extent, so that the electrochemical performance of the composite electrode material is improved.
Preferably, prior to said dispersing said acid-treated CNTs in an alcoholic solvent, further comprises: a dispersant is added to an alcohol solvent. Wherein the alcohol solvent is one of ethanol, glycol and butanol; the dispersing agent is one of polyvinylpyrrolidone (PVP), sodium dodecyl benzene sulfonate, sodium dodecyl sulfate and sodium hexadecyl polyoxyethylene ether phosphate. More preferably, the dispersant is polyvinylpyrrolidone and the alcohol solvent is ethanol. The dispersing agent is added to better disperse the CNTs in the alcohol solvent, so that a substrate is coated more uniformly.
Preferably, the LLOs @ LATP @ CNTs composite material is obtained after drying, the drying temperature is 60-90 ℃, and ethanol remained on the product is rapidly volatilized.
The present invention also provides a composite electrode material comprising: the lithium-rich layered oxide comprises a lithium-rich layered oxide, titanium aluminum lithium phosphate coated on the lithium-rich layered oxide, and a carbon nano tube coated on the titanium aluminum lithium phosphate.
The composite electrode material can be prepared by the preparation method. Meanwhile, the LLOs @ LATP @ CNTs composite material has a porous spherical core-shell structure, so that the specific surface area of an electrode material can be greatly increased, and the performances of the composite electrode material, such as conductivity, cycling stability, specific capacity and the like, can be improved.
Preferably, the mass percent of the carbon nanotubes in the positive electrode composite material is 1% -5%, and the composite electrode material has good electrochemical performance.
As shown in FIG. 1(a), the LLOs is a porous spherical structure, the porous spherical structure is formed by stacking a plurality of LLOs nanoparticles, and the invention forms a core-shell structure by coating LATP outside the porous spherical LLOs and then coating CNTs. LATP as a lithium ion conductor and CNTs as an electron conductor synergistically improve the electrical conductivity of the composite material. And the porous spherical structure forms a three-dimensional structure, and the LLOs is a nanoparticle, so that the specific surface area is higher, and the lithium ions can be conveniently inserted and extracted.
Specifically, communicated pore channels are formed in the three-dimensional structure, and the pore channels are filled with electrolyte, so that the electrolyte can be favorably infiltrated, and the electrolyte can be fully contacted with the material. The particle-nanocrystallized LLOs can shorten a lithium ion diffusion path, and on the basis, LATP can further improve the transmission of lithium ions, so that the rate capability of the material is improved. The CNTs are positioned on the surface of the shell-core structure, so that the electron transmission between two adjacent shell-core structures and between two adjacent three-dimensional structures can be facilitated, and the electron transmission performance of the whole material is improved.
By adopting a one-core two-shell structure, namely that the LLOs are sequentially coated with the LATP and the CNTs, the crystal phase transformation caused in the lithium ion embedding and de-embedding processes is favorably inhibited, so that the stability, the cycle performance and the coulombic efficiency of the material are improved. On the basis, the three-dimensional structure facilitates heat conduction, and particularly CNTs on the surface can facilitate heat conduction, so that 'hot spots' cannot be formed, the material cannot fail due to overheating, and the stability and the cycle performance of the material are further improved.
Example 1
1. Preparation of LLOs materials
Reacting LiOH2O、Mn(CH3COO3)2•4H2O、Ni(CH3COO3)2•4H2O、Co(CH3COO3)2•4H2O、H2C2O4Adding into ethanol water solution (molar ratio of ethanol to water is 1: 1), heating at 175 deg.C for 20 hr, washing with deionized water and ethanol, oven drying at 85 deg.C, and preparing Li1.2Mn0.54Ni0.13Co0.13O2Finally calcining the precursor powder at the high temperature of 750 ℃ to obtain the LLOs material.
2. Preparation of LLOs @ LATP composite Material
Reacting LiNO with a catalyst3、Al(NO3)3•9H2O、Ti(OC4H9)4、NH4H2PO4Adding C6H8O7Stirring the solution for 5 hours at 70 ℃ in the aqueous solution until the solution becomes clear to obtain Li1.4Al0.4Ti1.6(PO4)3Precursor sol of (LATP for short) and Li as Li-rich laminar anode material1.2Mn0.54Ni0.13Co0.13O2(LLOs for short), stirring at 90 ℃ for 5 h to evaporate the solvent, drying at 100 ℃ for 10 h to obtain a precursor of LLOs @ LATP, and calcining at 700 ℃ for 5 h to obtain the LLOs @ LATP composite material.
3. Preparation of LLOs @ CNTs composite material
The CNTs are heated and treated by mixed acid (the volume ratio of sulfuric acid to nitric acid in the mixed acid is 1: 3), and then washed by water to be neutral to obtain the CNTs treated by the acid. And then, taking PVP as a dispersing agent and ethanol as a solvent, stirring and ultrasonically dispersing the CNTs subjected to acid treatment for 40 min respectively, adding the lithium-rich layered positive electrode material LLOs, continuously and ultrasonically stirring for 40 min respectively, finally washing with ethanol, and drying at 70 ℃ to obtain the LLOs @ CNTs composite material.
4. Preparation of LLOs @ LATP @ CNTs composite material
The CNTs are heated and treated by mixed acid (the volume ratio of sulfuric acid to nitric acid in the mixed acid is 1: 3), and then washed by water to be neutral to obtain the CNTs treated by the acid. And then, stirring and ultrasonically dispersing the acid-treated CNTs for 30 min by using PVP as a dispersing agent and ethanol as a solvent, adding the LLOs @ LATP prepared in the step two, continuously and ultrasonically stirring for 30 min respectively, finally washing with ethanol, and drying at 70 ℃ to obtain the LLOs @ LATP @ CNTs composite material.
The prepared composite material of the LLOs @ LATP, the LLOs @ CNTs, the LLOs @ LATP @ CNTs and the LLOs material are characterized.
Fig. 1 and 2 are SEM and TEM images of the four electrode materials in this example, respectively. In FIGS. 1 and 2, the drawing (a) is LLOs, the drawing (b) is LLOs @ CNTs, the drawing (c) is LLOs @ LATP, and the drawing (d) is LLOs @ LATP @ CNTs. Fig. 3 is a graph of rate performance for four electrode materials in this example. Fig. 4 is a graph of the cycling performance of the four electrode materials in this example at a current density of 0.2C.
The SEM and TEM images in FIGS. 1-2 substantially show that the coating material in the three composites, LLOs @ CNTs, LLOs @ LATP, LLOs @ LATP @ CNTs, is uniformly distributed on the surface of the matrix LLOs. The rate performance graphs and the cycle performance graphs of the four electrode materials under the current density of 0.2C in the figures 3-4 respectively show that the LLOs @ LATP @ CNTs composite material has the best rate performance, the highest capacity and the most stable cycle performance, and the electrochemical performance of the composite material is greatly improved compared with that of an unmodified LLOs material.
Table 1 shows the specific surface area data of the four materials prepared in this example. As can be seen from table 1: the specific surface area of LLOs @ LATP @ CNTs was the largest compared to the other three materials. With reference to fig. 1 and fig. 2, the LLOs @ LATP @ CNTs composite material prepared by the present invention has a porous spherical structure, and meanwhile, the porous spherical structure is combined with a double-layer coated core-shell structure of the composite material, such that a specific surface area of the prepared composite material can be greatly increased, and the improvement of properties of mass transfer, heat transfer, and the like of the composite electrode material is facilitated, such that the composite material exhibits characteristics of high electrical conductivity, good cycling stability, and high specific capacity.
TABLE 1 data of specific surface area of four materials prepared in example 1
Example 2
1. Preparation of LLOs @ LATP composite Material
Reacting LiNO with a catalyst3、Al(NO3)3•9H2O、Ti(OC4H9)4、NH4H2PO4Adding C6H8O7Stirring in water solution at 50 deg.C for 3 hr until the solution becomes clear to obtain Li1.4Al0.4Ti1.6(PO4)3Precursor sol of (LATP for short) and Li as Li-rich laminar anode material1.2Mn0.54Ni0.13Co0.13O2(prepared by example 1), stirring at 70 ℃ for 8h to evaporate the solvent, drying at 80 ℃ for 14h to obtain a precursor LLOs @ LATP, and calcining at 600 ℃ for 6 h to obtain the LLOs @ LATP composite material.
2. Preparation of LLOs @ LATP @ CNTs composite material
The CNTs are heated and treated by mixed acid (the volume ratio of sulfuric acid to nitric acid in the mixed acid is 1: 3), and then washed by water to be neutral to obtain the CNTs treated by the acid. And stirring and ultrasonically dispersing the acid-treated CNTs for 10 min by using PVP as a dispersing agent and ethanol as a solvent, adding the product LLOs @ LATP prepared in the step one, continuously and ultrasonically stirring for 50 min respectively, finally washing with ethanol, and drying at 65 ℃ to obtain the LLOs @ LATP @ CNTs composite material.
Example 3
1. Preparation of LLOs @ LATP composite Material
Reacting LiNO with a catalyst3、Al(NO3)3•9H2O、Ti(OC4H9)4、NH4H2PO4Adding C6H8O7Stirring for 1 h at 90 ℃ in the aqueous solution until the solution becomes clear to obtain Li1.4Al0.4Ti1.6(PO4)3Precursor sol of (LATP for short) and Li as Li-rich laminar anode material1.2Mn0.54Ni0.13Co0.13O2(prepared from example 1), stirring at 95 ℃ for 4h to evaporate the solvent, drying at 140 ℃ for 6 h to obtain a precursor LLOs @ LATP, and calcining at 850 ℃ for 4h to obtain the LLOs @ LATP composite material.
2. Preparation of LLOs @ LATP @ CNTs composite material
The CNTs are heated and treated by mixed acid (the volume ratio of sulfuric acid to nitric acid in the mixed acid is 1: 3), and then washed by water to be neutral to obtain the CNTs treated by the acid. And stirring and ultrasonically dispersing the acid-treated CNTs for 45 min by using PVP as a dispersing agent and ethanol as a solvent, adding the LLOs @ LATP prepared in the step one, continuously and ultrasonically stirring for 45 min respectively, finally washing with ethanol, and drying at 80 ℃ to obtain the LLOs @ LATP @ CNTs composite material.
Based on the problems of capacity attenuation and voltage reduction caused by side reaction, crystal phase transformation, oxygen loss and the like of the lithium ion battery anode material-lithium-rich layered anode material with high specific capacity and the electrolyte in the charging and discharging processes, the anode material is coated with a fast ion conductor with high ionic conductivity, a solid electrolyte LATP and an electronic conductor CNTs with high electronic conductivity in a double-layer mode, so that the overall conductivity of the material (both the electronic conductivity and the ionic conductivity are improved) can be improved while the structural transformation of the material and the side reaction with the electrolyte are inhibited and the oxidative decomposition of the electrolyte is slowed down, the problems of capacity attenuation and voltage reduction of the material are further relieved, and the electrochemical performance of the material is improved.
It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.
Claims (5)
1. A preparation method of a composite electrode material is characterized by comprising the following steps:
preparing a LLOs @ LATP composite material;
adding CNTs into a mixed acid solution, heating, washing the CNTs with water to be neutral to obtain acid-treated CNTs, wherein the mixed acid solution is a mixed solution of sulfuric acid and nitric acid, and the volume ratio of the sulfuric acid to the nitric acid in the mixed acid solution is 1: 3;
dispersing the CNTs subjected to acid treatment in an alcohol solvent, adding the LLOs @ LATP composite material, then performing ultrasonic stirring, washing a product with ethanol, and drying at 60-90 ℃ to obtain the LLOs @ LATP @ CNTs composite material, wherein the LLOs @ LATP @ CNTs composite material is of a porous spherical core-shell structure, and the method further comprises the following steps of: adding a dispersing agent into an alcohol solvent;
the preparation of the LLOs @ LATP composite material comprises the following steps:
adding lithium nitrate, aluminum nitrate, tetrabutyl titanate and ammonium dihydrogen phosphate into a citric acid aqueous solution, and stirring at 50-100 ℃ until the solution becomes clear to obtain a precursor sol of lithium aluminum titanium phosphate;
adding lithium-rich layered oxide into the precursor sol of the lithium aluminum titanium phosphate, stirring at 70-110 ℃ for 3-8h to evaporate the solvent, drying at 80-150 ℃ for 5-14h to obtain a precursor LLOs @ LATP, and calcining at 500-900 ℃ for 3-7h to obtain a composite LLOs @ LATP material;
the preparation method of the lithium-rich layered oxide comprises the following steps:
reacting LiOH & H2O、Mn(CH3COO3)2·4H2O、Ni(CH3COO3)2·4H2O、Co(CH3COO3)2·4H2O、H2C2O4Adding into ethanol water solution, heating at 150-200 deg.C for 15-24h, washing the obtained product with water and ethanol, and drying at 70-100 deg.C to obtain LLOs precursor powder;
and calcining the LLOs precursor powder at the high temperature of 900 ℃ of 500-.
2. The method for preparing the composite electrode material according to claim 1, wherein the alcohol solvent is one of ethanol, ethylene glycol and butanol.
3. The method for preparing the composite electrode material according to claim 1, wherein the dispersant is one of polyvinylpyrrolidone, sodium dodecylbenzenesulfonate, sodium dodecylsulfate, and sodium hexadecylpolyoxyethylene ether phosphate.
4. A composite electrode material, comprising: the lithium-rich layered oxide comprises a lithium-rich layered oxide, titanium aluminum lithium phosphate coated on the lithium-rich layered oxide, and a carbon nano tube coated on the titanium aluminum lithium phosphate; the composite electrode material is prepared by the preparation method of the composite electrode material according to any one of claims 1 to 3.
5. The composite electrode material according to claim 4, wherein the mass percentage of the carbon nanotubes in the composite electrode material is 1% to 5%.
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| CN111987297B (en) * | 2020-08-26 | 2022-06-24 | 北京理工大学重庆创新中心 | Lithium-rich manganese-based positive electrode material with aluminum-doped surface and coated with lithium aluminum titanium phosphate and preparation method thereof |
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