CN108172780B - Alkali metal secondary battery negative electrode active material and preparation method thereof - Google Patents
Alkali metal secondary battery negative electrode active material and preparation method thereof Download PDFInfo
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Abstract
The invention belongs to the field of electrochemical power sources, and particularly relates to an alkali metal secondary battery negative electrode active material and a preparation method thereof. The negative active material is of a fully-coated spherical core-shell structure, the shell is nano titanium dioxide, and the core comprises nano ferric oxide; the mass ratio of the iron element to the titanium element is 5-15: 1. the unique core-shell structure of the material is beneficial to relieving volume expansion in the charge and discharge process and maintaining the structural stability of the active material in the circulation process. Meanwhile, the nano iron particles generated in situ are beneficial to improving the electronic conductance of the material and accelerating the electron transfer among active substance particles. The material is used as an alkali metal secondary battery cathode active material, has multiple characteristics of high capacity, high cycle stability and the like under the condition of not introducing a conductive agent carbon source, and is a novel energy storage battery cathode active material with low price and environmental friendliness.
Description
Technical Field
The invention belongs to the field of electrochemical power sources, and particularly relates to an alkali metal secondary battery negative electrode active material and a preparation method thereof.
Background
In recent years, with the popularization of energy storage systems such as electric vehicles and smart grids, people have more urgent needs for high-energy-density secondary battery systems. The alkali metal secondary battery mainly includes a lithium ion secondary battery, a sodium ion secondary battery, and the like. The lithium ion secondary battery has the advantages of high voltage, high capacity, high power density, long cycle life, no memory effect and the like, and is widely applied to the fields of portable electronic equipment, electric automobiles, national defense industry, portable electronic equipment and the like. However, the lithium ion secondary battery has problems of high cost, short service life, potential safety hazard and the like, and in addition, the storage of lithium resources is very limited, so that the large-scale application of the lithium ion secondary battery is limited to a great extent.
The research on the sodium ion secondary battery is started almost at the same time as the lithium ion secondary battery, but its development is very difficult. As early as the eighties of the last century, research on positive and negative electrode materials of sodium ion secondary batteries has been conducted, but almost all of the attempts have been disappointed. The main reason is that the early anode and cathode material systems related to the sodium storage reaction are mostly simply transplanted with the material structure successfully applied in the lithium ion secondary battery, and the special requirements of the sodium storage reaction on the main crystal lattice structure are not fully considered.
The main reported negative electrode materials of alkali metal secondary batteries mainly include alkali metals, amorphous carbon materials, graphitic carbon materials, alkali metal alloys and metal oxides. Alkali metals as negative electrode materials are prone to generate dendrites during charge-discharge cycles, thereby causing safety problems such as short circuits. The electrochemical performance of graphite carbon materials as negative electrodes of lithium ion secondary batteries is greatly related to the degree of graphitization, and graphite cannot be used as a carbon negative electrode for sodium ion batteries due to the problem of interlayer spacing. The amorphous carbon material has the best sodium storage effect, but the specific surface area degree has great influence on the electrochemical performance. When the alkali metal alloy is used as the cathode of the alkali secondary battery, the volume expansion is large, and the circulation stability is poor. The problems of serious volume expansion, low electronic conductivity and unstable cycle of the metal oxide used as the cathode of the alkali secondary battery also occur.
Titanium dioxide is a potentialThe alkali metal secondary battery cathode material has the advantages of low working voltage, good chemical stability, high natural abundance and low cost. The titanium dioxide has a multi-dimensional tunnel structure, can be embedded with alkali metal ions and used as a cathode material, and TiO with different tunnel structures2Exhibit different sodium intercalation or lithium intercalation properties. Huang (J.P.Huang, D.Yuan, H.Z.Zhang, Y.L.Cao, G.R.Li, H.X.Yang, X.P.Gao, Electrochemical sodium storage of TiO2(B)nanotubes for sodium ion batteries[J]RSC Advances,3(2013) 12593-12597), etc. prepared layered monoclinic phase TiO2(B) The (001) crystal face of the nanotube has 0.56nm interlayer spacing, is suitable for the intercalation and deintercalation of sodium ions, and has 80mAh g at 3.0-0.8V-1The reversible specific capacity of (a). Wu (l.m.wu, d.brewer, d.buchholz, g.a.gifin, c.r.castro, a.ochel, s.passerini, underfolding the Mechanism of Sodium insert in enzyme TiO2Nanoparticles[J]Adv. energy Mater.,5(2015) 1401142), et al prepared anatase TiO2Can realize 0.41Na (140mAh g)-1) The low ion diffusion rate and low intrinsic electron conductivity limit their performance. In addition, anatase titanium dioxide is considered a zero strain material during lithium deintercalation. Transition metal oxides such as ferroferric oxide are a kind of secondary battery negative electrodes with conversion reaction, have the characteristics of high theoretical capacity, environmental friendliness and the like, but have the problem of poor cycle performance due to collapse of volume expansion structures in the electrochemical reaction of lithium or sodium intercalation and deintercalation. Therefore, the search for a negative electrode material with stable structure, high capacity, high coulombic efficiency, good cycling stability and low price is the key of the alkali metal secondary battery in energy storage and practical application.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a negative active material for an alkali metal secondary battery. The cathode active material has a stable core-shell structure, the outer titanium dioxide can play a role in buffering volume change in the charging and discharging process, and the cycle stability of the alkali metal secondary battery is improved. Meanwhile, the nano ferric oxide particles and the nano iron particles generated in situ by sintering in the air improve the electronic conductivity of the material and solve the problem of poor rate capability of the material.
The second purpose of the invention is to provide a preparation method of the alkali metal secondary battery cathode active material, which adopts the reflux reaction and hydrothermal reaction which are environment-friendly, simple and easy to realize, and the sol-gel process of in-situ coating titanium dioxide, and forms the material with stable core-shell structure through the low-temperature sintering of the precursor.
In order to achieve the purpose, the technical scheme of the invention is as follows:
the negative active material of the alkali metal secondary battery is a fully-coated spherical core-shell structure, the shell is nano titanium dioxide, and the core comprises nano ferric oxide; the mass ratio of the iron element to the titanium element is 5-15: 1.
preferably, the spherical particle size of the anode active material is 200-300 nm.
Preferably, the nano titania shell has an amorphous structure or an anatase structure.
Preferably, the thickness of the nano titanium dioxide shell is 5-100 nm.
Preferably, the core is a mixture of nano ferric oxide and nano iron particles, and the nano iron particles are distributed on the outermost layer of the core.
The invention relates to a preparation method of an alkali metal secondary battery negative electrode active material, which comprises the following steps:
(1) dissolving a surfactant in ethylene glycol, wherein the concentration of the surfactant is as follows: 0.1-2g/L, magnetically stirring for 30-360min to dissolve; under magnetic stirring, adding ferric salt, and continuously stirring until the ferric salt is completely dissolved for a period of time to obtain a mixed solution 1;
(2) carrying out reflux reaction on the mixed solution 1 at 60-220 ℃ for 30-360min at the stirring speed of 200-1200r/min, carrying out hydrothermal reaction at 120-180 ℃ for 6-24h after the reaction is finished, centrifuging, washing the precipitate with ethanol, and drying at 60-80 ℃ to obtain precursor particles;
(3) dissolving titanium salt in ethanol, wherein the mass ratio of the titanium salt to the ethanol is 1:4-8, so as to obtain a mixed solution 2;
(4) dissolving the precursor particles obtained in the step (2) in the mixed solution 2, wherein the mass ratio of the precursor particles to the mixed solution 2 is 3-10:1, and stirring at 60-120 ℃ until ethanol is completely volatilized to obtain an intermediate product;
(5) sintering the intermediate product at the temperature of 300-600 ℃ for 1-6h, wherein the heating rate is 1-5 ℃/min, and obtaining the cathode active material of the alkali metal secondary battery.
Preferably, the surfactant is polyvinylpyrrolidone-K30 (PVP-K30), cetyltrimethylammonium bromide (CTAB) or ethylenediaminetetraacetic acid (EDTA).
Preferably, the iron salt is Fe (NO)3)3·9H2O or FeCl3。
Preferably, the titanium salt is titanium isopropoxide, tetrabutyl titanate or titanium tetrachloride.
The negative active material of the sodium ion secondary battery is the negative active material of the alkali metal secondary battery.
The invention relates to a lithium ion secondary battery, wherein the negative active material of the battery is the negative active material of the alkali metal secondary battery.
Advantageous effects
1. The invention provides a negative electrode active material of an alkali metal secondary battery, wherein a zero-strain titanium dioxide nano shell uniformly coats nano ferric oxide particles to form a two-dimensional core-shell structure, and further, nano ferric particles generated in situ in a thermal sintering process are uniformly distributed outside the ferric oxide nano particles to form a three-dimensional core-shell structure. The unique two-dimensional or three-dimensional core-shell structure is beneficial to relieving volume expansion in the charge and discharge process and maintaining the structural stability of the active material in the circulation process. Meanwhile, the nano ferric oxide and the nano iron particles generated in situ are beneficial to improving the electronic conductivity of the material and accelerating the electron transfer among the active substance particles. The material is used as an alkali metal secondary battery cathode active material, has multiple characteristics of high capacity, high cycle stability and the like under the condition of not introducing a conductive agent carbon source, and is a novel energy storage battery cathode active material with low price and environmental friendliness.
2. The invention provides a preparation method of a negative active material of an alkali metal secondary battery, which is characterized in that a spherical iron oxide precursor is generated in situ by controlling the reflux temperature, the reflux time, the hydrothermal temperature and the hydrothermal time. In the reaction process, the reflux temperature is controlled at 60-220 ℃, and the reflux reaction time is 30-360 min; the temperature is too high, the reaction time is too short, and spherical precursor particles with uniform appearance and surface active agent complexation cannot be obtained; the reaction time is too long when the temperature is too low, the surfactant can not generate uniform and stable complex reaction, and the agglomeration of precursor particles is serious. The hydrothermal reaction temperature is controlled at 180 ℃, the hydrothermal reaction time is 6-24h, when the temperature is too low and the time is too short, the iron oxide nanoparticles grow unevenly, and when the temperature is too high and the time is too long, the grown iron oxide nanoparticles are seriously agglomerated; spherical precursor particles with uniform dispersion and morphology cannot be obtained. The addition of hydrothermal reaction during the reflux reaction and sol-gel reaction is an important step in obtaining a stable spherical structure. The raw materials used in the method are substances which are widely distributed in nature, low in price and environment-friendly, the preparation method is simple, the cost is low, the method is green and environment-friendly, the material performance is more stable, and mass production is easy to realize.
Drawings
Fig. 1 is a scanning electron microscope image of the precursor particles prepared in example 1.
Fig. 2 is a distribution diagram of iron element of the negative active material for alkali metal secondary battery obtained in example 1.
Fig. 3 is a distribution diagram of iron element of the negative active material for alkali metal secondary battery obtained in example 1.
FIG. 4 is a distribution diagram of titanium element in the negative active material of alkali metal secondary battery obtained in example 1.
Fig. 5 is a graph showing an oxygen distribution of the anode active material for an alkali metal secondary battery obtained in example 1.
Fig. 6 is a transmission electron microscope photograph of the negative active material of the alkali metal secondary battery obtained in example 1.
Fig. 7 is an X-ray diffraction pattern of the negative active material for an alkali metal secondary battery prepared in example 1.
Fig. 8 is a charge-discharge curve of the sodium ion secondary battery in example 1 for the first 20 weeks.
Fig. 9 is a graph showing rate performance of the sodium ion secondary battery in example 1.
Fig. 10 is a charge-discharge curve of the lithium ion secondary battery in example 1 for the first 20 weeks.
Fig. 11 is a graph showing rate performance of the lithium ion secondary battery in example 1.
Fig. 12 is a graph showing the cycle characteristics of the sodium ion secondary battery in example 2.
Detailed Description
The present invention will be described in further detail with reference to specific examples.
Assembling the alkali metal secondary battery:
(1) assembling the sodium ion secondary battery:
mixing the final product prepared in the example with acetylene black and a binding agent polyvinylidene fluoride (PVDF) according to a weight ratio of 8:1:1, adding an N-methylpyrrolidone (NMP) solution, grinding in a normal-temperature drying environment to form slurry, then uniformly coating the slurry on a current collector copper foil, drying, cutting into electrode plates with the diameter of 1cm, drying at 80 ℃ for 12 hours under a vacuum condition, and transferring into a glove box for later use. The button cell takes metal sodium as an electrode and NaPF6Dissolving in mixed solution of Ethylene Carbonate (EC) and diethyl carbonate (DEC) (EC/DEC volume ratio of 1: 1) to obtain electrolyte, NaPF6The concentration is 1.0mol/L, and the CR2032 button cell is assembled.
(2) Assembling the lithium ion secondary battery:
mixing the final product prepared in the embodiment with acetylene black and a binder PVDF according to a weight ratio of 8:1:1, adding an NMP solution, grinding in a normal-temperature drying environment to form slurry, then uniformly coating the slurry on a current collector copper foil, cutting into pole pieces with the diameter of 1cm after drying, drying at 80 ℃ for 12 hours under a vacuum condition, and transferring into a glove box for later use. The button cell takes metal sodium as an electrode and NaPF6Dissolving in mixed solution of Ethylene Carbonate (EC) and diethyl carbonate (DEC) (EC/DEC volume ratio of 1: 1) to obtain electrolyte, NaPF6The concentration is 1.0mol/L, and the CR2032 button cell is assembled.
Negative active materials of alkali metal secondary batteries prepared in the following examples and assembled alkali metal secondary batteries were respectively tested as follows:
(1) scanning Electron Microscope (SEM) testing of precursor particles: the sample preparation process comprises the following steps: and uniformly coating the dry powder on the conductive adhesive, performing gold plating treatment to enhance the conductivity of the material, and after the gold spraying treatment, sending the material into a sample chamber for observing the appearance of the material. The acceleration voltage was 20KV using a field emission scanning electron microscope (FEI, quandata 200 f).
(1) Element distribution of the negative electrode active material:
the preparation process of the sample comprises the following steps: and (3) adding absolute ethyl alcohol into the sample powder, performing ultrasonic dispersion to obtain a sample suspension, dripping the suspension liquid to a copper grid or a carbon film by using a dropper, vacuumizing, drying and then sending the sample to a sample chamber for observation. The model of the instrument is HRTEM, Tecnai G2F 20S-TWIN, 200 KV.
(2) Negative active material Transmission Electron Microscope (TEM) test:
the preparation process of the sample comprises the following steps: and (3) adding absolute ethyl alcohol into the sample powder, performing ultrasonic dispersion to obtain a sample suspension, dripping the suspension liquid to a copper grid or a carbon film by using a dropper, vacuumizing, drying and then sending the sample to a sample chamber for observation. The model of the instrument is HRTEM, Tecnai G2F 20S-TWIN, 200 KV.
(3) Negative active material X-ray diffraction (XRD) test:
the crystal structure of the material is characterized by using an X-ray diffractometer with the model of Rigaku Ultima IV-185, Co K alpha is a radioactive source,
the tubing pressure was 40kV and the tubing flow was 35 mA. The test process is as follows: pressing the uniformly ground powder sample into a glass sample groove, then placing the glass sample groove on a sample rack of an X-ray diffractometer for testing, wherein the scanning range is 10-90 DEG, and the scanning speed is 1.5-8 DEG min-1。
(4) The negative electrode active material is used as a sodium ion secondary battery negative electrode, and the charge-discharge curve is 20 weeks before the charge-discharge at 0.1C:
constant current charge and discharge test is carried out by adopting a Land battery test system, and the current density is highDegree of 25mA g-1The voltage interval is 0.001-2.5V.
(5) And (3) testing the multiplying power performance of the negative electrode of the sodium ion secondary battery by using the negative electrode active material:
constant current charge and discharge test is carried out by adopting a Land battery test system, and the current density is 25mA g-1，50mA g-1，100mA g-1，200mA g-1，500mA g-1，1A g-1The voltage interval is 0.001-2.5V.
(6) The negative electrode active material is used as a lithium ion battery negative electrode, and the charge-discharge curve is 20 weeks before charge-discharge at 0.1C:
constant current charge and discharge test is carried out by adopting a Land battery test system, and the current density is 50mA g-1The voltage interval is 0.001-2.5V.
(7) And (3) testing the multiplying power performance of the negative electrode of the lithium ion secondary battery by using the negative electrode active material:
constant current charge and discharge test is carried out by adopting a Land battery test system, and the current density is 50mA g-1，100mA g-1，200mA g-1，500mA g-1，1A g-1，2A g-1，5A g-1The voltage interval is 0.001-2.5V.
Example 1
This example is intended to illustrate the preparation of the negative active material of the present invention and its application in sodium ion secondary batteries and lithium ion secondary batteries, and comprises the following specific steps:
(1) weighing 30mg of PVP-K30 as a surfactant, dissolving in 60ml of ethylene glycol solvent, and magnetically stirring for 360min to dissolve; 30mg of Fe (NO) were added with magnetic stirring3)3·9H2O, continuously stirring for 2 hours to obtain a mixed solution 1;
(2) transferring the mixed solution 1 into a three-neck flask, putting the three-neck flask into an oil bath pot, adding condensed water for refluxing, controlling the stirring speed to be 600r/min, refluxing and reacting at 90 ℃ for 90min, transferring the mixed solution into a reaction kettle after the reaction is finished, sealing, reacting at 180 ℃ for 12h, centrifuging, washing precipitates with ethanol, and drying at 60 ℃ to obtain precursor particles.
(3) Weighing 100mg of titanium isopropoxide, and dissolving in 30ml of ethanol to obtain a mixed solution 2;
(4) dissolving 50mg of precursor particles in the mixed solution 2, and stirring at 60 ℃ until ethanol volatilizes to obtain an intermediate product 1.
(5) And sintering the intermediate product 1 for 2h at 450 ℃ in an air atmosphere, wherein the heating and cooling rate is 2 ℃/min, and obtaining a final product, namely the alkali metal secondary battery cathode active material.
The result of SEM test on the precursor particles is shown in fig. 1, and the precursor particles are uniformly dispersed and uniform in morphology.
The final product is subjected to element analysis, the element distribution is shown in figure 2, and the elements in the final product are distributed in a core-shell structure. The distribution of Fe element is shown in FIG. 3, the Fe element is uniformly distributed at the center of the sphere; the Ti element is distributed as shown in figure 4, and is uniformly distributed on the outer layer of the spherical structure; the distribution of the O element is shown in FIG. 5, and the O element is uniformly distributed in the spherical structure.
The final product was subjected to TEM test, and the result is shown in FIG. 6, in which the final product has an obvious core-shell structure, the particle size of the material is 200-250nm, and the thickness of the nano-titania coating layer is 50-80 nm.
XRD test is carried out on the final product, and the result is shown in figure 7, and the iron and the ferric oxide peaks are obvious; the presence of titanium dioxide is evidenced by a small peak at 30 °.
Elemental analysis, TEM test and XRD test of the final product show that the final product is a fully-coated spherical core-shell structure, the shell is nano titanium dioxide, and the core is nano ferric oxide and nano iron.
The performance test of the final product assembled sodium ion secondary battery is carried out, and the results are as follows:
the 0.1C charge-discharge curve is shown in FIG. 8, and the first week discharge capacity can reach 385mAh g-1The first week coulombic efficiency was 83.92%.
The results of the rate capability test are shown in FIG. 9, where the current is 1A g-1The discharge capacity per hour reaches 160mAh g-1Coulombic efficiency>99%, it was found that the negative electrode active material for alkali metal secondary batteries exhibited excellent electrochemical performance without introducing conductive carbon when used as a negative electrode for sodium ion secondary batteries.
The performance test was performed on the final product assembled lithium ion secondary battery:
the 0.1C charge-discharge curve is shown in FIG. 10, and the first week discharge capacity can reach 1212.9mAh g-1Capacity after 20 weeks of circulation 999.1mAh g-1。
The results of the rate capability test are shown in FIG. 11, where the current is 5A g-1The discharge capacity per hour reaches 201.6mAh g-1Coulombic efficiency>99%, and it can be seen that when the current returns to a small current, the reversible capacity rises back. It is thus understood that the negative electrode active material for an alkali metal secondary battery exhibits excellent electrochemical performance without introducing conductive carbon when used as a negative electrode for a lithium ion secondary battery.
Comparative example 1
This example is presented to illustrate the preparation of negative active materials that are not coated with nano-titania and their use in sodium ion secondary batteries.
(1) Weighing 30mg of PVP-K30 as a surfactant, dissolving in 60ml of ethylene glycol solvent, and magnetically stirring for 360min to dissolve;
(2) 30mg of Fe (NO) were added under magnetic stirring3)3·9H2Adding O into the solvent in the step (1), and continuously stirring for 2 h;
(3) transferring the solution in the step (2) into a three-neck flask, putting the three-neck flask into an oil bath pot, adding condensed water for refluxing, controlling the stirring speed to be 600r/min, carrying out reflux reaction at 90 ℃ for 90min, transferring the solution into a reaction kettle after the reaction is finished, sealing, reacting at 180 ℃ for 12h, centrifuging, washing with ethanol, and drying at 60 ℃ to obtain precursor particles.
Sintering the obtained precursor particles for 2h at 450 ℃ in an air atmosphere, wherein the heating and cooling rate is 2 ℃/min, and obtaining a final product after heat treatment.
The performance of the final product assembled lithium ion secondary battery was tested, and the result is shown in FIG. 12, in which the first cycle charge capacity under the 0.1C charge-discharge test was 159.6mAh g-1The coulombic efficiency was 33.35%. The discharge capacity after 70 weeks of cycling was 86.1mAh g-1。
By comparison with example 1, it was found that the alkali metal secondary battery assembled using one of the alkali metal secondary battery negative electrode active materials described in example 1 exhibited high reversible capacity, high rate performance.
The invention includes, but is not limited to, the above embodiments, and any equivalent substitutions or partial modifications made under the spirit and principle of the invention are deemed to be within the scope of the invention.
Claims (9)
1. An alkali metal secondary battery negative electrode active material characterized in that: the cathode active material is of a fully-coated spherical core-shell structure, the shell is nano titanium dioxide, the core is a mixture of nano ferric oxide and nano iron particles, and the nano iron particles are distributed on the outermost layer of the core; the mass ratio of the iron element to the titanium element is 5-15: 1;
the preparation method of the negative active material of the alkali metal secondary battery comprises the following steps:
(1) dissolving surfactant in ethylene glycol, wherein the concentration of the surfactant is 0.1-2g/L, and magnetically stirring for 30-360min to dissolve the surfactant; under magnetic stirring, adding ferric salt, and continuously stirring until the ferric salt is completely dissolved for a period of time to obtain a mixed solution 1;
(2) carrying out reflux reaction on the mixed solution 1 at 60-220 ℃ for 30-360min at the stirring speed of 200-1200r/min, carrying out hydrothermal reaction at 120-180 ℃ for 6-24h after the reaction is finished, centrifuging, washing the precipitate with ethanol, and drying at 60-80 ℃ to obtain precursor particles;
(3) dissolving titanium salt in ethanol, wherein the mass ratio of the titanium salt to the ethanol is 1:4-8, so as to obtain a mixed solution 2;
(4) dissolving the precursor particles obtained in the step (2) in the mixed solution 2, wherein the mass ratio of the precursor particles to the mixed solution 2 is 3-10:1, and stirring at 60-120 ℃ until ethanol is completely volatilized to obtain an intermediate product;
(5) sintering the intermediate product at the temperature of 300-600 ℃ for 1-6h, wherein the heating rate is 1-5 ℃/min, and obtaining the cathode active material of the alkali metal secondary battery.
2. The negative active material for an alkali metal secondary battery as claimed in claim 1, wherein: the spherical particle size of the anode active material was 200-300 nm.
3. The negative active material for an alkali metal secondary battery as claimed in claim 1, wherein: the nano titanium dioxide shell is in an amorphous structure or an anatase structure.
4. The negative active material for an alkali metal secondary battery as claimed in claim 1, wherein: the thickness of the nano titanium dioxide shell is 5-100 nm.
5. A method for preparing the negative active material for alkali metal secondary batteries according to any one of claims 1 to 4, characterized in that: the method comprises the following steps:
(1) dissolving surfactant in ethylene glycol, wherein the concentration of the surfactant is 0.1-2g/L, and magnetically stirring for 30-360min to dissolve the surfactant; under magnetic stirring, adding ferric salt, and continuously stirring until the ferric salt is completely dissolved for a period of time to obtain a mixed solution 1;
(2) carrying out reflux reaction on the mixed solution 1 at 60-220 ℃ for 30-360min at the stirring speed of 200-1200r/min, carrying out hydrothermal reaction at 120-180 ℃ for 6-24h after the reaction is finished, centrifuging, washing the precipitate with ethanol, and drying at 60-80 ℃ to obtain precursor particles;
(3) dissolving titanium salt in ethanol, wherein the mass ratio of the titanium salt to the ethanol is 1:4-8, so as to obtain a mixed solution 2;
(4) dissolving the precursor particles obtained in the step (2) in the mixed solution 2, wherein the mass ratio of the precursor particles to the mixed solution 2 is 3-10:1, and stirring at 60-120 ℃ until ethanol is completely volatilized to obtain an intermediate product;
(5) sintering the intermediate product at the temperature of 300-600 ℃ for 1-6h, wherein the heating rate is 1-5 ℃/min, and obtaining the cathode active material of the alkali metal secondary battery.
6. The method of claim 5, wherein the method comprises the steps of: the surfactant is polyvinylpyrrolidone-K30, cetyl trimethyl ammonium bromide or ethylene diamine tetraacetic acid.
7. The method of claim 5, wherein the method comprises the steps of: the iron salt is Fe (NO)3)3·9H2O or FeCl3(ii) a The titanium salt is titanium isopropoxide, tetrabutyl titanate or titanium tetrachloride.
8. A sodium ion secondary battery characterized in that: the negative electrode active material for the battery is the negative electrode active material for the alkali metal secondary battery according to any one of claims 1 to 4.
9. A lithium ion secondary battery characterized in that: the negative electrode active material for the battery is the negative electrode active material for the alkali metal secondary battery according to any one of claims 1 to 4.
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| CN106348251A (en) * | 2016-08-22 | 2017-01-25 | 东南大学 | Method for preparing monodisperse oxide nanoparticles |
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