CN108172780B - A kind of negative electrode active material of alkali metal secondary battery and preparation method thereof - Google Patents

Abstract

The invention belongs to the field of electrochemical power sources, and in particular relates to a negative electrode active material of an alkali metal secondary battery and a preparation method thereof. The negative electrode active material is a fully coated spherical core-shell structure, the shell is nano-titanium dioxide, and the core includes nano-iron trioxide; the mass ratio of iron element to titanium element is 5-15:1. The unique core-shell structure of the material helps alleviate the volume expansion during charging and discharging and maintains the structural stability of the active material during cycling. At the same time, the in-situ generated nano-iron particles help to improve the electronic conductivity of the material and accelerate the electron transfer between the active material particles. The material, as the negative electrode active material of alkali metal secondary batteries, has multiple characteristics such as high capacity and high cycle stability without introducing a carbon source of conductive agent, and is a new type of low-cost and environmentally friendly negative electrode for energy storage batteries. active material.

Description

A kind of negative electrode active material of alkali metal secondary battery and preparation method thereof

technical field

The invention belongs to the field of electrochemical power sources, and in particular relates to a negative electrode active material of an alkali metal secondary battery and a preparation method thereof.

Background technique

In recent years, with the promotion of energy storage systems such as electric vehicles and smart grids, the demand for high-energy-density secondary battery systems has become more urgent. Alkali metal secondary batteries mainly include lithium ion secondary batteries, sodium ion secondary batteries, and the like. Li-ion secondary batteries have the advantages of high voltage, high capacity, high power density, long cycle life and no memory effect, and are widely used in portable electronic devices, electric vehicles, defense industry, and portable electronic devices. However, lithium-ion secondary batteries have problems such as high cost, short life, and safety hazards. In addition, the storage of lithium resources is very limited, which largely limits the large-scale application of lithium-ion secondary batteries.

Research on sodium ion secondary batteries started almost at the same time as lithium ion secondary batteries, but its development was very difficult. As early as the 1980s, people have carried out research on anode and cathode materials for sodium ion secondary batteries, but almost all attempts have ended in disappointment. This is mainly due to the fact that most of the early cathode and anode material systems related to sodium storage reaction simply transplant the material structure successfully applied in lithium-ion secondary batteries, without fully considering the special requirements of the sodium storage reaction for the host lattice structure.

At present, the main alkaline metal secondary battery anode materials reported are mainly alkali metals, amorphous carbon materials, graphitic carbon materials, alkali metal alloys and metal oxides. Alkali metals as anode materials are prone to dendrites during charge-discharge cycles, causing safety problems such as short circuits. When graphitic carbon material is used as the negative electrode of lithium ion secondary battery, the electrochemical performance has a great relationship with the degree of graphitization, while graphite cannot be used as the carbon negative electrode of sodium ion battery due to the problem of interlayer spacing. Amorphous carbon materials have the best sodium storage effect, but the degree of specific surface area has a great influence on the electrochemical performance. When the alkali metal alloy is used as the negative electrode of the alkaline secondary battery, the volume expansion is large, resulting in poor cycle stability. Metal oxides as negative electrodes of alkaline secondary batteries also suffer from severe volume expansion, low electronic conductance, and unstable cycling.

Titanium dioxide is a potential anode material for alkaline metal secondary batteries due to its low operating voltage, good chemical stability, high natural abundance and low cost. Titanium dioxide has a multi-dimensional tunnel structure, which can intercalate alkali metal ions. As a negative electrode material, _TiO2 with different tunnel structures exhibits different sodium or lithium intercalation properties. J.Huang(JPHuang,D.Yuan,HZZhang,YLCao,GRLi,HXYang,XPGao,Electrochemical sodiumstorage of TiO ₂ (B) nanotubes for sodium ion batteries[J],RSC Advances,3(2013)12593-12597.) etc. Layered monoclinic TiO ₂ (B) nanotubes were prepared with (001) planes with 0.56 nm interlayer spacing, suitable for intercalation and deintercalation of sodium ions, with a reversible specific capacity of 80 mAh g ^-1 at 3.0-0.8 V . L.Wu(LMWu,D.Bresser,D.Buchholz,GAGiffin,CRCastro,A.Ochel,S.Passerini,Unfolding the Mechanism of Sodium Insertion in Anatase TiO ₂ Nanoparticles[J],Adv.EnergyMater.,5(2015)1401142 .) et al. prepared anatase TiO ₂ , which can achieve intercalation and deintercalation of 0.41Na (140mAh g ^-1 ), but the low ionic diffusion rate and low intrinsic electronic conductivity limit its performance. In addition, anatase TiO2 is considered to be a zero-strain material during the lithium-deintercalation process. Transition metal oxides, such as ferric oxide, are a kind of secondary battery negative electrode with conversion reaction, which has the characteristics of high theoretical capacity and environmental friendliness. The volume expansion structure collapses, leading to the problem of poor cycle performance. Therefore, finding a negative electrode material with stable structure, high capacity, high coulombic efficiency, good cycle stability and low price is the key to the energy storage and practical application of alkali metal secondary batteries.

SUMMARY OF THE INVENTION

In view of this, one object of the present invention is to provide a negative electrode active material for an alkali metal secondary battery. The negative electrode active material has a stable core-shell structure, and the outer layer of titanium dioxide can play the role of buffering the volume change during charging and discharging, thereby improving the cycle stability of the alkali metal secondary battery. At the same time, the in-situ sintered nano-iron trioxide particles and nano-iron particles in the air improve the electronic conductivity of the material and solve the problem of poor rate performance of the material.

The second purpose of the present invention is to provide a method for preparing a negative electrode active material for an alkali metal secondary battery, which adopts an environmentally friendly and easy-to-implement reflux reaction and a hydrothermal reaction and a sol-gel process of in-situ coating of titanium dioxide, Materials with stable core-shell structures are formed by low-temperature sintering of precursors.

For achieving the above object, technical scheme of the present invention is as follows:

A negative electrode active material for an alkali metal secondary battery, the negative electrode active material is a fully covered spherical core-shell structure, the shell is nano-titanium dioxide, and the core comprises nano-iron trioxide; the mass ratio of iron element to titanium element is 5- 15:1.

Preferably, the spherical particle size of the negative electrode active material is 200-300 nm.

Preferably, the nano titanium dioxide 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-iron trioxide and nano-iron particles, and the nano-iron particles are distributed in the outermost layer of the core.

A preparation method of the negative electrode active material of an alkali metal secondary battery according to the present invention, the method steps are as follows:

(1) Dissolve the surfactant in ethylene glycol, the concentration of the surfactant is: 0.1-2g/L, and magnetically stir it for 30-360min to dissolve it; under the magnetic stirring, add iron salt, and continue stirring until it is completely dissolved for a period of time , to obtain mixed solution 1;

(2) The mixed solution 1 was refluxed for 30-360min at 60-220℃, and the stirring speed was 200-1200r/min. After the reaction, hydrothermally reacted at 120-180℃ for 6-24h, centrifuged, and the precipitate was washed with ethanol Then, drying at 60-80 °C to obtain precursor particles;

(3) dissolving the titanium salt in ethanol, the mass ratio of the titanium salt and the ethanol is 1:4-8 to obtain the mixed solution 2;

(4) Dissolving the precursor particles obtained in step (2) in the mixed solution 2, the mass ratio of the precursor particles to the mixed solution 2 is 3-10:1, and stirring at 60-120° C. until the ethanol is completely volatilized to obtain an intermediate product ;

(5) sintering the intermediate product at 300-600° C. for 1-6 hours, and the heating rate is 1-5° C./min, to obtain a negative electrode active material for an 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 ·9H ₂ O or FeCl ₃ .

Preferably, the titanium salt is titanium isopropoxide, tetrabutyl titanate or titanium tetrachloride.

A sodium ion secondary battery, wherein the negative electrode active material of the battery is the negative electrode active material of an alkali metal secondary battery according to the present invention.

A lithium ion secondary battery, wherein the negative electrode active material of the battery is the negative electrode active material of an alkali metal secondary battery according to the present invention.

beneficial effect

1. The present invention provides a negative electrode active material for an alkali metal secondary battery. The zero-strain titanium dioxide nanoshell evenly coats the nano-iron trioxide particles to form a two-dimensional core-shell structure. The iron nanoparticles are uniformly distributed on the outside of the iron oxide nanoparticles, forming a three-dimensional core-shell structure. This unique 2D or 3D core-shell structure helps alleviate the volume expansion during charge-discharge and maintains the structural stability of the active material during cycling. At the same time, the in-situ-generated nano-iron trioxide and nano-iron particles help to improve the electronic conductance of the material and accelerate the electron transfer between the active material particles. The material, as the negative electrode active material of alkali metal secondary batteries, has multiple characteristics such as high capacity and high cycle stability without introducing a carbon source of conductive agent, and is a new type of low-cost and environmentally friendly negative electrode for energy storage batteries. active material.

2. The present invention provides a method for preparing a negative electrode active material of an alkali metal secondary battery, wherein a spherical iron oxide precursor is generated in situ by controlling the reflux temperature and the reflux time, as well as the hydrothermal temperature and time. During the reaction, the reflux temperature was controlled at 60-220°C, and the reflux reaction time was 30-360min; if the temperature was too high, the reaction time was too short, and the spherical precursor particles complexed with surfactants with uniform morphology could not be obtained; if the temperature was too low, the reaction If the time is too long, the surfactant cannot have a uniform and stable complexation reaction, and the precursor particles agglomerate seriously. The temperature of the hydrothermal reaction is controlled at 120-180°C, and the hydrothermal reaction time is 6-24h. When the temperature is too low and the time is too short, the growth of iron oxide nanoparticles is uneven, and the temperature is too high and the time is too long, and the grown iron oxide nanoparticles are seriously agglomerated; The spherical precursor particles with uniform dispersion and morphology could not be obtained. The addition of hydrothermal reaction during reflux reaction and sol-gel reaction is an important step to obtain stable spherical structures. The raw materials used in the method are all widely distributed in nature, cheap and environmentally friendly, the preparation method is simple, the cost is low, the green environmental protection, the material properties are more stable, and the mass production is easy to be realized.

Description of drawings

FIG. 1 is a scanning electron microscope image of the precursor particles prepared in Example 1. FIG.

FIG. 2 is a diagram showing the distribution of iron elements in the negative electrode active material of the alkali metal secondary battery prepared in Example 1. FIG.

FIG. 3 is a diagram showing the distribution of iron elements in the negative electrode active material of the alkali metal secondary battery prepared in Example 1. FIG.

FIG. 4 is a diagram showing the distribution of titanium elements in the negative electrode active material of the alkali metal secondary battery prepared in Example 1. FIG.

FIG. 5 is a diagram showing the distribution of oxygen elements in the negative electrode active material of the alkali metal secondary battery prepared in Example 1. FIG.

6 is a transmission electron microscope image of the negative electrode active material for an alkali metal secondary battery prepared in Example 1. FIG.

FIG. 7 is an X-ray diffraction pattern of the negative electrode active material of the alkali metal secondary battery prepared in Example 1. FIG.

8 is a charge-discharge curve of the sodium-ion secondary battery in Example 1 in the first 20 weeks.

FIG. 9 is a graph showing the 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 in the first 20 weeks.

11 is a graph showing the rate performance of the lithium ion secondary battery in Example 1. FIG.

FIG. 12 is a graph showing the cycle performance of the sodium ion secondary battery in Example 2. FIG.

Detailed ways

The present invention will be described in further detail below with reference to specific embodiments.

Assembly of Alkali Metal Secondary Battery:

(1) Assembly of sodium ion secondary battery:

The final product prepared in the example is mixed with acetylene black and binder polyvinylidene fluoride (PVDF) according to the weight ratio of 8:1:1, N-methylpyrrolidone (NMP) solution is added, and the solution is dried at room temperature. Then, the slurry was uniformly coated on the current collector copper foil. After drying, it was cut into electrode sheets with a diameter of 1 cm. After drying at 80 °C for 12 h under vacuum conditions, it was transferred to a glove box for use. The button battery uses sodium metal as the electrode, and NaPF ₆ is dissolved in a mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) (the volume ratio of EC to DEC is 1:1) to prepare the electrolyte, NaPF ₆ The concentration was 1.0mol/L, and it was assembled into a CR2032 button cell.

(2) Assembly of lithium ion secondary battery:

The final product prepared in the example is mixed with acetylene black and binder PVDF in a weight ratio of 8:1:1, NMP solution is added, and the slurry is ground in a dry environment at room temperature to form a slurry, and then the slurry is uniformly coated on On the current collector copper foil, cut into pole pieces with a diameter of 1 cm after drying. After drying at 80 °C for 12 h under vacuum conditions, they were transferred to a glove box for use. The button battery uses sodium metal as the electrode, and NaPF ₆ is dissolved in a mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) (the volume ratio of EC to DEC is 1:1) to prepare the electrolyte, NaPF ₆ The concentration was 1.0mol/L, and it was assembled into a CR2032 button cell.

The negative electrode active materials of the alkali metal secondary batteries prepared in the following examples and the assembled alkali metal secondary batteries were respectively tested as follows:

(1) Scanning Electron Microscope (SEM) test of precursor particles: The sample preparation process is as follows: the dry powder is uniformly coated on the conductive adhesive, and gold-plated to enhance the conductivity of the material. After gold spraying, it is sent to the sample chamber for material morphology observation. A field emission scanning electron microscope (FEI, Quanata 200f) was used with an accelerating voltage of 20KV.

(1) Element distribution of negative electrode active material:

The preparation process of the sample is as follows: take the sample powder, add absolute ethanol, ultrasonically disperse to obtain the sample suspension, use a dropper to take the suspension drop to the copper grid or carbon film, vacuum dry and then send it to the sample chamber for observation. The instrument model is HRTEM, TecnaiG2 F20 S-TWIN, 200KV.

(2) Transmission electron microscope (TEM) test of negative electrode active material:

The preparation process of the sample is as follows: take the sample powder, add absolute ethanol, ultrasonically disperse to obtain the sample suspension, use a dropper to take the suspension drop to the copper grid or carbon film, vacuum dry and then send it to the sample chamber for observation. The instrument model is HRTEM, TecnaiG2 F20 S-TWIN, 200KV.

(3) X-ray diffraction (XRD) test of negative electrode active material:

管压为40kV，管流为35mA。测试过程为：将研磨均匀的粉末样品压制与玻璃样品槽中，然后置于X射线衍射仪样品架上进行测试，扫描范围为10°～90°，扫描速度为1.5～8°min^-1。The crystal structure of the material was characterized using an X-ray diffractometer, model Rigaku Ultima IV-185, with Co Kα as the radioactive source,

The tube pressure is 40kV and the tube flow is 35mA. The test process is as follows: the uniformly ground powder sample is pressed into the glass sample tank, and then placed on the sample holder of the X-ray diffractometer for testing. The scanning range is 10°～90°, and the scanning speed is 1.5～8°min ^-1 .

(4) The negative electrode active material is used as the negative electrode of the sodium ion secondary battery, and the charge-discharge curve for the first 20 weeks is charged and discharged at 0.1C:

The constant current charge-discharge test was carried out by using the Land battery test system, the current density was 25mA g ^-1 , and the voltage range was 0.001-2.5V.

(5) The negative rate performance test of the negative electrode active material for sodium ion secondary battery:

The galvanostatic charge-discharge test was carried out by using the Land battery test system, the current density was 25mA g ^-1 , 50mA g ^-1 , 100mA g ^-1 , 200mA g ^-1 , 500mA g ^-1 , 1A g ^-1 , and the voltage range was 0.001-2.5 V.

(6) The negative electrode active material is used as the negative electrode of the lithium ion battery. The charge-discharge curve for the first 20 weeks at 0.1C:

The constant current charge-discharge test was carried out by using the Land battery test system, the current density was 50mA g ^-1 , and the voltage range was 0.001-2.5V.

(7) The negative electrode active material is used for the negative rate performance test of the lithium ion secondary battery:

The galvanostatic charge-discharge test was carried out using the Land battery test system, and the current density was 50mA g ^-1 , 100mA g ^-1 , 200mA g ^-1 , 500mA g ^-1 , 1A g ^-1 , 2A g ^-1 , 5A g ^-1 , The voltage range is 0.001-2.5V.

Example 1

This example is used to illustrate the preparation of the negative electrode active material of the present invention and its application in sodium ion secondary batteries and lithium ion secondary batteries, and the specific steps are:

(1) Weigh 30 mg of surfactant PVP-K30 and dissolve it in 60 ml of ethylene glycol solvent, and stir it magnetically for 360 min to dissolve it; under magnetic stirring, add 30 mg of Fe(NO ₃ ) ₃ ·9H ₂ O, and continue stirring for 2h , to obtain mixed solution 1;

(2) transfer the mixed solution 1 into the three-necked flask and put it into the oil bath pot, add condensed water to reflux, control the stirring speed to be 600 r/min, perform a reflux reaction at 90 ° C for 90 min, transfer to the reaction kettle after the reaction, and seal the , reacted at 180 °C for 12 h, centrifuged, washed the precipitate with ethanol, and dried at 60 °C to obtain precursor particles.

(3) take by weighing 100mg of titanium isopropoxide and be dissolved in 30ml of ethanol to obtain mixed solution 2;

(4) 50 mg of precursor particles were dissolved in mixed solution 2, and stirred at 60° C. until ethanol was volatilized to obtain intermediate product 1.

(5) The intermediate product 1 is sintered at 450° C. for 2 hours in an air atmosphere, and the temperature rise and fall rate is 2° C./min to obtain the final product, that is, a negative electrode active material for an alkali metal secondary battery.

The SEM test of the precursor particles is carried out, and the results are shown in Figure 1. The precursor particles are uniformly dispersed and have a uniform morphology.

Elemental analysis was performed on the final product, and its element distribution was shown in Figure 2. The elements in the final product showed a core-shell structure distribution. The distribution of Fe elements is shown in Figure 3, and the Fe elements are evenly distributed in the center of the sphere; the distribution of Ti elements is shown in Figure 4, and the Ti elements are evenly distributed in the outer layer of the spherical structure; the distribution of O elements is shown in Figure 5, and the O elements are evenly distributed in a spherical structure.

The final product was tested by TEM, and the results are shown in Figure 6. The final product has obvious core-shell structure characteristics, and the particle size of the material is 200-250 nm, and the thickness of the nano-titania coating layer is 50-80 nm.

The final product is subjected to XRD test, and the results are shown in Figure 7. The peak shapes of iron and ferric oxide are obvious; the small peak at 30° proves the existence of titanium dioxide.

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-iron trioxide and nano-iron.

The performance test of the sodium-ion secondary battery assembled by the final product is carried out, and the results are as follows:

The 0.1C charge-discharge curve is shown in Fig. 8, the first-week discharge capacity can reach 385mAh g ^-1 , and the first-week Coulombic efficiency is 83.92%.

The rate performance test results are shown in Figure 9. When the current is 1A g ^-1 , the discharge capacity reaches 160mAh g ^-1 , and the Coulomb efficiency is >99%. It can be seen that the negative electrode active material of the alkali metal secondary battery is a sodium ion secondary battery. When used as the negative electrode of secondary battery, it can show good electrochemical performance without introducing conductive carbon.

The performance test of the lithium-ion secondary battery assembled by the final product:

The 0.1C charge-discharge curve is shown in Fig. 10, the discharge capacity in the first cycle can reach 1212.9mAh g ^-1 , and the capacity after 20 cycles of cycling is 999.1mAh g ^-1 .

The rate performance test results are shown in Figure 11. When the current is 5A g ^-1 , the discharge capacity reaches 201.6mAh g ^-1 , and the Coulomb efficiency is >99%, and it can be seen that when the current returns to a small current, the reversible capacity recovers. It can be seen that the negative electrode active material of the alkali metal secondary battery can exhibit good electrochemical performance without introducing conductive carbon when used as the negative electrode of the lithium ion secondary battery.

Comparative Example 1

This example is used to illustrate the preparation of the negative electrode active material that is not coated with nano-titania and its application in sodium ion secondary batteries.

(1) Weigh 30mg of surfactant PVP-K30 and dissolve it in 60ml of ethylene glycol solvent, and magnetically stir it for 360min to dissolve it;

(2) Under magnetic stirring, 30 mg of Fe(NO ₃ ) ₃ ·9H ₂ O was added to the solvent of step (1), and the stirring was continued for 2 h;

(3) transfer the solution of step (2) into the three-necked flask and put it in the oil bath pot, add condensed water to reflux, control the stirring speed to be 600r/min, reflux reaction at 90 ° C for 90min, transfer to the reactor after the reaction is completed , sealed, reacted at 180 °C for 12 h, centrifuged, washed with ethanol, and dried at 60 °C to obtain precursor particles.

The obtained precursor particles were sintered at 450°C for 2 hours in an air atmosphere, and the heating and cooling rate was 2°C/min, and the final product was obtained after heat treatment.

The performance test of the lithium-ion secondary battery assembled by the final product is carried out. The results are shown in Figure 12. Under the 0.1C charge-discharge test, the first-week charging capacity is 159.6mAh g ^-1 , and the coulombic efficiency is 33.35%. The discharge capacity after 70 cycles was 86.1 mAhg ^-1 .

By comparing with Example 1, it is found that the alkali metal secondary battery assembled by using the negative electrode active material of the alkali metal secondary battery described in Example 1 exhibits high reversible capacity and high rate performance.

The invention includes but is not limited to the above embodiments, and any equivalent replacement or partial improvement made under the spirit and principle of the present invention will be deemed to be within the protection scope of the present invention.

Claims (9)

1. an alkaline metal secondary battery negative electrode active material, it is characterized in that: described negative electrode active material is the spherical core-shell structure of full coating, and shell is nano titanium dioxide, and core is the mixture of nano iron ferric oxide and nano iron particles , the nano-iron particles are distributed in the outermost layer of the core; the mass ratio of iron to titanium is 5-15:1; The steps of the preparation method of the negative electrode active material of the alkaline metal secondary battery are as follows: (1) Dissolve the surfactant in ethylene glycol, the concentration of the surfactant is 0.1-2g/L, and magnetically stir it for 30-360min to dissolve it; under magnetic stirring, add iron salt, and continue stirring until it is completely dissolved for a period of time, to obtain mixed solution 1; (2) The mixed solution 1 was refluxed for 30-360min at 60-220℃, and the stirring speed was 200-1200r/min. After the reaction, hydrothermally reacted at 120-180℃ for 6-24h, centrifuged, and the precipitate was washed with ethanol Then, drying at 60-80 °C to obtain precursor particles; (3) dissolving the titanium salt in ethanol, the mass ratio of the titanium salt and the ethanol is 1:4-8 to obtain the mixed solution 2; (4) Dissolving the precursor particles obtained in step (2) in the mixed solution 2, the mass ratio of the precursor particles to the mixed solution 2 is 3-10:1, and stirring at 60-120° C. until the ethanol is completely volatilized to obtain an intermediate product ; (5) sintering the intermediate product at 300-600° C. for 1-6 hours, and the heating rate is 1-5° C./min, to obtain a negative electrode active material for an alkali metal secondary battery. 2 . The negative electrode active material for an alkali metal secondary battery according to claim 1 , wherein the spherical particle size of the negative electrode active material is 200-300 nm. 3 . 3 . The negative electrode active material for an alkaline metal secondary battery according to claim 1 , wherein the nano-titania shell is an amorphous structure or an anatase structure. 4 . 4 . The negative electrode active material for an alkaline metal secondary battery according to claim 1 , wherein the thickness of the nano titanium dioxide shell is 5-100 nm. 5 . 5. A method for preparing a negative electrode active material for an alkaline metal secondary battery according to any one of claims 1 to 4, wherein the method steps are as follows: (1) Dissolve the surfactant in ethylene glycol, the concentration of the surfactant is 0.1-2g/L, and magnetically stir it for 30-360min to dissolve it; under magnetic stirring, add iron salt, and continue stirring until it is completely dissolved for a period of time, to obtain mixed solution 1; (2) The mixed solution 1 was refluxed for 30-360min at 60-220℃, and the stirring speed was 200-1200r/min. After the reaction, hydrothermally reacted at 120-180℃ for 6-24h, centrifuged, and the precipitate was washed with ethanol Then, drying at 60-80 °C to obtain precursor particles; (3) dissolving the titanium salt in ethanol, the mass ratio of the titanium salt and the ethanol is 1:4-8 to obtain the mixed solution 2; (4) Dissolving the precursor particles obtained in step (2) in the mixed solution 2, the mass ratio of the precursor particles to the mixed solution 2 is 3-10:1, and stirring at 60-120° C. until the ethanol is completely volatilized to obtain an intermediate product ; (5) sintering the intermediate product at 300-600° C. for 1-6 hours, and the heating rate is 1-5° C./min, to obtain a negative electrode active material for an alkali metal secondary battery. 6. The preparation method of a negative electrode active material for an alkali metal secondary battery as claimed in claim 5, wherein the surfactant is polyvinylpyrrolidone-K30, cetyltrimethylammonium bromide or Ethylenediaminetetraacetic acid. 7 . The method for preparing a negative electrode active material for an alkali metal secondary battery according to claim 5 , wherein: the iron salt is Fe(NO ₃ ) ₃ .9H ₂ O or FeCl ₃ ; the titanium salt is: 8 . It is titanium isopropoxide, tetrabutyl titanate or titanium tetrachloride. 8 . A sodium ion secondary battery, wherein the negative electrode active material of the battery is the negative electrode active material of an alkali metal secondary battery according to any one of claims 1 to 4 . 9 . A lithium ion secondary battery, wherein the negative electrode active material of the battery is the negative electrode active material of an alkali metal secondary battery according to any one of claims 1 to 4 .

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