阅读说明：本技术 一种微波法制备超小氧化物与碳复合的锂电池负极材料的方法 (Method for preparing lithium battery cathode material compounded by ultra-small oxide and carbon by microwave method ) 是由 黄小萧 刘力铭 卫增岩 段小明 张洪磊 贾德昌 于 2020-05-15 设计创作，主要内容包括：一种微波法制备超小氧化物与碳复合的锂电池负极材料的制备方法。本发明属于锂离子电池负极材料的制备领域。本发明为解决现有锂离子电池容量及导电性等综合性能不高,且制备工艺较复杂,成本较高的技术问题。本发明方法如下：一、配置盐溶液使金属离子渗入金属-有机框架材料(MOF)；利用抽滤将渗离子的MOF材料与溶液分离,烘干得到渗离子的MOF材料；二、将渗离子的MOF材料和石墨烯使混合后研磨,然后微波短时间加热；三、产物经过洗涤除杂后得到超小氧化物与碳复合的锂电池负极材料。本发明产品的纳米颗粒尺寸为2～10nm,在低氧化物负载下就可具有高容量表现。(A method for preparing a lithium battery cathode material compounded by ultra-small oxide and carbon by a microwave method. The invention belongs to the field of preparation of lithium ion battery cathode materials. The invention aims to solve the technical problems of low comprehensive performance such as capacity, conductivity and the like, complex preparation process and high cost of the conventional lithium ion battery. The method comprises the following steps: firstly, preparing a salt solution to enable metal ions to permeate into a metal-organic framework Material (MOF); separating the ion-permeated MOF material from the solution by suction filtration, and drying to obtain the ion-permeated MOF material; secondly, mixing the ion-permeated MOF material and graphene, grinding, and then heating by microwave for a short time; and thirdly, washing and removing impurities from the product to obtain the lithium battery cathode material compounded by the ultra-small oxide and the carbon. The product has the nano-particle size of 2-10 nm, and can have high capacity performance under the load of a low oxide.)

1. A method for preparing a lithium battery cathode material compounded by ultra-small oxide and carbon by a microwave method is characterized by comprising the following steps:

firstly, soaking Zn-based MOF in a metal salt solution under the stirring condition, continuously stirring to obtain a mixed solution, and drying a solid phase after suction filtration to obtain ion-permeated MOF powder;

secondly, mixing the ion-permeated MOF powder with graphene powder, grinding, and then carrying out microwave heating on the ground product to obtain mixed powder;

and thirdly, carrying out acid washing impurity removal or alkali washing impurity removal on the mixed powder obtained in the second step, carrying out suction filtration, and then drying to obtain the ultra-small oxide and carbon composite lithium battery cathode material.

2. The method for preparing the ultra-small oxide and carbon composite lithium battery anode material through the microwave method according to claim 1, wherein in the step one, the Zn-based MOF is ZIF-1, ZIF-2, ZIF-3, ZIF-4, ZIF-6, ZIF-7, ZIF-8, ZIF-10 or ZIF-11.

3. The method for preparing the lithium battery anode material compounded by the ultra-small oxide and the carbon according to the claim 1, wherein the metal salt solution in the step one is an aqueous solution of a metal salt or an N-methyl pyrrolidone solution of a metal salt, and the metal salt is a chloride of Mn, Fe, Ni, Co, Cu and Sn or an acetate of Mn, Fe, Ni, Co, Cu and Sn.

4. The method for preparing the lithium battery anode material compounded by the ultra-small oxide and the carbon according to the claim 1, wherein the concentration of the metal salt in the metal salt solution in the step one is 0.04mol/L to 0.5 mol/L.

5. The method for preparing the lithium battery anode material compounded by the ultra-small oxide and the carbon according to the claim 1, wherein the stirring parameters in the step one are as follows: the rotating speed is 300 rpm-1200 rpm, and the time is 2 min-10 min; the soaking time in the step one is 0.5 to 3 hours; and in the step one, the suction filtration time is 0.2-2 h.

6. The method for preparing the lithium battery anode material compounded by the ultra-small oxide and the carbon according to the claim 1, wherein the drying parameters in the step one are as follows: the drying temperature is 30-60 ℃, and the drying time is 2-15 h.

7. The method for preparing the ultra-small oxide and carbon composite lithium battery negative electrode material through the microwave method according to claim 1, wherein the mass ratio of the ion-infiltrated MOF powder to the graphene powder in the second step is (10-1): 1.

8. The method for preparing the lithium battery anode material compounded by the ultra-small oxide and the carbon according to the claim 1, wherein the grinding time in the step two is 5-60 min; in the second step, the microwave heating power is 500W-1000W, and the time is 3 s-60 s.

9. The method for preparing the lithium battery anode material compounded by the ultra-small oxide and the carbon according to the claim 1, wherein the acid washing and impurity removing processes in the third step are as follows: soaking the mixed powder in an acid solution for 1-2 h to complete impurity removal, wherein the acid solution is a nitric acid solution or a hydrochloric acid solution, and the concentration of the acid solution is 0.5-3 mol/L; the process of alkali washing and impurity removal in the third step is as follows: and soaking the mixed powder in an alkali solution for 2-5 h to complete impurity removal, wherein the alkali solution is a sodium hydroxide solution or a potassium hydroxide solution, and the concentration of the alkali solution is 0.5-3 mol/L.

10. The method for preparing the ultra-small oxide and carbon composite lithium battery anode material according to claim 1, wherein the concrete process of suction filtration in the third step is as follows: adding water for suction filtration for 2-3 times after the first suction filtration, wherein the suction filtration is carried out for 2-10 min each time; the drying parameters in the third step are as follows: the drying temperature is 30-60 ℃, and the drying time is 0.5-2 h.

Technical Field

The invention belongs to the field of preparation of lithium ion battery cathode materials; in particular to a method for preparing a lithium battery cathode material compounded by ultra-small oxide and carbon by a microwave method.

Background

The lithium ion battery has the advantages of high energy density, environmental protection, small memory effect and the like, so that the lithium ion battery is widely applied to small-sized equipment such as mobile phones and cameras and also serves as a core energy storage component of electric automobiles. The application of the lithium ion battery is beneficial to reducing the use of fossil energy, thereby promoting the solution of energy crisis and environmental problems and promoting sustainable development. The development of lithium ion batteries is an important issue nowadays, and the key point is to improve the battery performance by using material design.

The electrode material is the core key point influencing the performance of the lithium ion battery, the negative electrode material used in the current commerce is mainly a graphite material, and the theoretical specific capacity of the graphite negative electrode material is 372 mAh/g. The low electrode potential of the graphite negative electrode material is easy to generate lithium dendrite, so that the safety is influenced, and meanwhile, the low capacity of the graphite material cannot meet the future development under the dual requirements of the current situation and policy.

Metal oxide negative electrode materials such as SnO₂、Fe₂O₃(and some bimetallic oxides such as ZnCo)₂O₄) Etc. have high theoretical specific capacity and suitable operating voltage is not easy to generate lithium dendrite, but these oxides have poor conductivity and generate large volume expansion in the lithium storage process.

On the particle structure, the nano design is often adopted, so that the particles have larger specific surface area, the reaction rate and the utilization rate of materials are improved, but the preparation process of the nano particles is often high in cost, complex in process and poor in stability. Further optimization is therefore required to improve the electrochemical performance of the anode material.

Disclosure of Invention

The invention provides a method for preparing a lithium battery cathode material compounded by ultra-small oxide and carbon by a microwave method, aiming at solving the technical problems of low comprehensive performance such as capacity, conductivity and the like, complex preparation process and high cost of the existing lithium battery.

The method for preparing the lithium battery cathode material compounded by the ultra-small oxide and the carbon by the microwave method comprises the following steps:

firstly, soaking Zn-based MOF in a metal salt solution under the stirring condition, continuously stirring to obtain a mixed solution, and drying a solid phase after suction filtration to obtain ion-permeated MOF powder;

secondly, mixing the ion-permeated MOF powder with graphene powder, grinding, and then carrying out microwave heating on the ground product to obtain mixed powder;

and thirdly, carrying out acid washing impurity removal or alkali washing impurity removal on the mixed powder obtained in the second step, carrying out suction filtration, and then drying to obtain the ultra-small oxide and carbon composite lithium battery cathode material.

Further defined, in the first step, the Zn-based MOF is ZIF-1, ZIF-2, ZIF-3, ZIF-4, ZIF-6, ZIF-7, ZIF-8, ZIF-10 or ZIF-11.

Further, the metal salt solution in the first step is an aqueous solution of a metal salt or an N-methyl pyrrolidone solution of a metal salt, and the metal salt is a chloride of Mn, Fe, Ni, Co, Cu, Sn or an acetate of Mn, Fe, Ni, Co, Cu, Sn.

Further, the concentration of the metal salt in the metal salt solution in the step one is 0.04 mol/L-0.5 mol/L.

Further, the stirring parameters in the first step are as follows: the rotating speed is 300rpm to 1200rpm, and the time is 2min to 10 min.

Further limiting, the soaking time in the step one is 0.5-3 h.

Further limiting, the suction filtration time in the step one is 0.2 h-2 h.

Further defined, the drying parameters in the first step are as follows: the drying temperature is 30-60 ℃, and the drying time is 2-15 h.

Further limiting, in the second step, the mass ratio of the ion-infiltrated MOF powder to the graphene powder is (10-1): 1.

Further limiting, the grinding time in the step two is 5 min-60 min.

Further limiting, the power of the microwave heating in the step two is 500W-1000W, and the time is 3 s-60 s.

Further limiting, the acid washing impurity removal process in the third step is as follows: and (3) soaking the mixed powder in an acid solution for 1-2 h to complete impurity removal, wherein the acid solution is a nitric acid solution or a hydrochloric acid solution, and the concentration of the acid solution is 0.5-3 mol/L.

Further limiting, the process of alkali washing and impurity removal in the third step is as follows: and soaking the mixed powder in an alkali solution for 2-5 h to complete impurity removal, wherein the alkali solution is a sodium hydroxide solution or a potassium hydroxide solution, and the concentration of the alkali solution is 0.5-3 mol/L.

Further limiting, the specific process of suction filtration in step three is as follows: and after the first suction filtration, adding water for suction filtration for 2-3 times, wherein the suction filtration is carried out for 2-10 min each time.

Further defined, the drying parameters in the third step are as follows: the drying temperature is 30-60 ℃, and the drying time is 0.5-2 h.

Compared with the prior art, the invention has the remarkable effects as follows:

1) the structure that the carbon-coated ultra-small oxide or the bimetallic oxide is compounded with the graphene is designed and prepared, so that the volume expansion can be relieved and the integral conductivity of the material can be improved on the basis of utilizing the height and capacity advantages of the oxide, and the novel structure is favorable for high capacity and cycling stability.

2) The precursor is obtained by adsorbing metal ions through the porous characteristic of a metal-organic framework (MOF), the metal ions are converted into ultra-small oxide nanoparticles after heating, the confinement effect of MOF gaps is favorable for nanocrystallization, the electrochemical reaction speed is increased, even the reversibility of the reaction is improved, the capacity expression is facilitated and improved, meanwhile, the MOF is also pyrolyzed to become carbon, and the purpose of making the best use of the substances is achieved.

3) For the preparation of the ultra-small oxide, the microwave method is rapid in heating, the process flow is shortened, the energy consumption is lower compared with the traditional heating mode, and the compound of the nano oxide particles can be prepared in batch.

4) The microwave method prepared by the method is used for preparing the lithium battery cathode material compounded by the ultra-small oxide and the carbon, wherein the oxide can be a single metal oxide or a double metal oxide; in appearance, a plurality of small nano oxide particles are coated by carbon to form submicron particles, and the submicron particles have a structure combining micro and nano.

5) The lithium battery cathode material compounded by the ultra-small oxide and the carbon prepared by the method has the advantages of simple and safe preparation process, rapidness and low cost, and is expected to be produced in a large scale.

6) The lithium battery cathode material compounded by the ultra-small oxide and the carbon prepared by the method is used as a lithium ion battery cathode material.

Drawings

FIG. 1 is an XRD pattern of ZIF-8 powder of tin-infiltrated ions obtained in step one and ZIF-8 used in embodiment one; wherein a is ZIF-8, and b is ZIF-8 powder of tin-penetrating ions;

FIG. 2 is an SEM photograph of a ZIF-8 powder of tin-infiltrated ions obtained in step one of the embodiments;

FIG. 3 is an SEM photograph of milled ZIF-8 and graphene of the tin-infiltrated ions in step two of the first embodiment;

FIG. 4 is an XRD spectrum of the lithium battery anode material compounded by graphene, ultra-small oxide and carbon according to the second step of the first embodiment; wherein a is graphene, and b is a lithium battery cathode material compounded by ultra-small oxide and carbon;

fig. 5 is an SEM photograph of the ultra small oxide and carbon composite lithium battery negative electrode material according to the first embodiment;

FIG. 6 is a TEM image of a lithium battery anode material compounded of an ultra-small oxide and carbon at 1 μm according to the first embodiment;

FIG. 7 is a TEM image of the ultra-small oxide and carbon composite lithium battery negative electrode material of the first embodiment at 50 nm;

FIG. 8 is a TEM image of the lithium battery anode material compounded by the ultra-small oxide and carbon of the first embodiment at 5 nm;

fig. 9 is an electron diffraction image of a lithium battery negative electrode material in which an ultra-small oxide is composited with carbon according to the first embodiment;

FIG. 10 is a thermogravimetric plot of a lithium battery anode material composited with ultra-small oxide and carbon according to the first embodiment;

fig. 11 is a Raman scattering spectrum of the lithium battery negative electrode material compounded by graphene, ultra-small oxide and carbon according to the second step of the first embodiment; wherein a is graphene, and b is a lithium battery cathode material compounded by ultra-small oxide and carbon;

fig. 12 is a charge and discharge curve of a lithium battery negative electrode material in which an ultra-small oxide is composited with carbon according to the first embodiment;

FIG. 13 is a cycle curve at 0.1A/g for a lithium battery anode material composited with ultra-small oxide and carbon according to the first embodiment;

fig. 14 is a rate test curve of the ultra-small oxide and carbon composite lithium battery negative electrode material according to the first embodiment.

Detailed Description

The first embodiment is as follows: the method for preparing the lithium battery cathode material compounded by the ultra-small oxide and the carbon by the microwave method comprises the following steps:

firstly, soaking 200mg of ZIF-8 in SnCl with the concentration of 0.22mol/L at the rotating speed of 600rpm₂·2H₂Soaking the O in N-methylpyrrolidone solution for 2h, continuously stirring for 5min at the rotating speed of 600rpm to obtain a mixed solution, performing suction filtration for 1h, and drying the solid phase at 60 ℃ for 12h to obtain the ZIF-8 powder of tin-infiltrated ions;

mixing 60mg of ZIF-8 powder of tin-infiltrated ions with 15mg of graphene powder, grinding for 20min, and heating the ground product at 750W for 3s to obtain mixed powder;

thirdly, placing the mixed powder obtained in the second step into a nitric acid solution to be soaked for 2 hours, removing impurities, performing suction filtration, and drying at 60 ℃ for 1 hour to obtain the lithium battery cathode material compounded by the ultra-small oxide and the carbon; the concentration of the nitric acid solution is 2 mol/L; the specific process of suction filtration is as follows: and after the first suction filtration, adding water for suction filtration for 3 times, and carrying out suction filtration for 5min each time.

Detecting (I): the XRD spectrogram of the ZIF-8 powder of the tin-infiltrated ions used in this embodiment and obtained in step one is shown in fig. 1, where a is ZIF-8 and b is ZIF-8 powder of the tin-infiltrated ions, and it can be seen from fig. 1 that after the tin ions are infiltrated, the derived peak strength of ZIF-8 is weakened, which indicates that a certain crystal structure change is brought about in the infiltration process.

And (2) detection: an SEM photograph of the ZIF-8 powder of the tin-infiltrated ions obtained in the first step of the present embodiment is shown in fig. 2, and it can be seen from fig. 2 that the square particle size of the ZIF-8 of the tin-infiltrated ions is about 0.5 μm, and the particles are agglomerated to some extent and combined into larger particles of about 2 μm.

And (3) detection: an SEM photograph of the milled ZIF-8 of the tin-infiltrated ion and graphene in the second step of the present embodiment is shown in fig. 3, and it can be seen from fig. 3 that the ZIF-8 particle of the tin-infiltrated ion is wrapped by the lamellar graphene, thereby achieving the recombination by simple milling. The graphene plays a role of a wave-absorbing auxiliary agent in the subsequent steps.

And (IV) detection: the XRD pattern of the graphene used in the second step of the present embodiment and the ultra-small oxide and carbon composite lithium battery anode material obtained in the present embodiment is shown in fig. 4, where a is graphene and b is the ultra-small oxide and carbon composite lithium battery anode material, and it can be seen from fig. 4 that the diffraction peak of the carbon-coated nano tin oxide and graphene composite material can correspond to graphene and cards 41-1445, which indicates that the material contains graphene and tin dioxide. The diffraction peak corresponding to tin dioxide has a larger full width at half maximum, indicating that the material has a smaller particle size.

And (5) detection: as shown in fig. 5, an SEM photograph of the lithium battery negative electrode material in which the ultra-small oxide and carbon are composited obtained in the present embodiment shows that a sheet-like graphene material supports a large number of particles, and these small particles correspond to the heat treatment product of ZIF-8 of tin-infiltrated ions.

And (6) detection: the TEM photographs of the ultra-small oxide and carbon composite lithium battery anode material obtained in the embodiment are shown in fig. 6 to 9, and the morphology of graphene composited with carbon-coated nano tin oxide with a size of about 0.5 μm can be seen from the macroscopic images 6 to 7, and the high resolution image in fig. 8 further determines that the nano tin oxide is about 5nm and is wrapped in the ZIF-8 carbonized product. The electron diffraction pattern in fig. 9 has diffraction rings corresponding to the (110) and (101) crystallographic planes of tin dioxide, further demonstrating the presence of tin dioxide.

And (5) detection (seventh): the thermogravimetric curve of the lithium battery cathode material compounded by the ultra-small oxide and the carbon obtained in the embodiment is shown in fig. 10, the lithium battery cathode material is heated in the air atmosphere, the temperature range is from room temperature to 1000 ℃, the mass is rapidly reduced in the process of 400-600 ℃, and the carbon material in the composite material is oxidized into carbon dioxide. From this it was determined that the mass of tin dioxide in the material was about 21% of the composite material.

And (eight) detection: the Raman scattering spectrum of the graphene used in the second step of the present embodiment and the ultra-small oxide and carbon composite lithium battery anode material finally obtained in the present embodiment is shown in fig. 11, and compared with the graphene, the Raman scattering spectrum of the D peak (1587.6 cm) of the carbon-coated nano tin oxide and graphene composite material^-1Position) and G peak (1355.0 cm)^-1Of) intensity ratio I_D/I_GThe decrease indicates that the graphene surface functional groups are further reduced during the heating process, and some of them probably participate in the reaction from tin ions to tin dioxide. In addition, compared with graphene, the 2D peak (2703.0 cm) of the carbon-coated nano tin oxide and graphene composite material^-1Where) was no longer evident, perhaps due to the presence of more ZIF-8 carbonization products in the material.

And (7) detection (nine): the charge-discharge curve of the ultra-small oxide and carbon composite lithium battery negative electrode material obtained in the embodiment is shown in fig. 12, the discharge/charge capacity of the first circle is 1056.1/638.4mAh/g, and thus the coulombic efficiency of the first circle is 60.44%. When the lithium ion battery is circulated to the 2 nd, 3 rd and 5 th circles, the specific discharge/charge capacity of the battery is 669.6/617.9, 648.9/612.7 and 633.6/606.8mAh/g respectively, and the capacity value gradually tends to be stable. From the charging curve part, a curve of-1 can be observed2V, 2.2V Presence platform, corresponding to Li, respectively_4.4Conversion of Sn to Sn and Sn to SnO₂The electrochemical reaction process of (1). The plateau is less pronounced because the tin dioxide has a very fast reaction rate due to its very small particle size.

Detection (ten): the cycle curve of the ultra-small oxide and carbon composite lithium battery negative electrode material obtained in the embodiment under 0.1A/g is shown in FIG. 13, the carbon-coated nano tin oxide and graphene composite material is slowly attenuated from the initial capacity of 630mAh/g to the 40 th circle, the capacity is reduced to 500mAh/g, which is probably caused by the influence of volume expansion on the particle structure, the capacity is slowly increased and is recovered to 586.1mAh/g when the carbon-coated nano tin oxide and graphene composite material reaches the 200 th circle, the capacity retention rate reaches 92.3%, and the lithium battery negative electrode material has better cycle stability. In the case of using only relatively low contents of SnO₂In this case, a higher capacity level is achieved.

Detection (eleven): the rate curve of the lithium battery negative electrode material compounded by the ultra-small oxide and the carbon obtained in the embodiment is shown in fig. 14, the current density is 0.1, 0.2, 0.5, 1, 2 and 5A/g in sequence in six stages from circle 1 to circle 60, and the corresponding capacity values are 690.3, 577.2, 455.4, 349.8, 242.1 and 105.6mAh/g respectively. When the current returns to 0.1A/g, the specific capacity returns to 511.6mAh/g rapidly. Finally, the specific capacity of the negative electrode material was 534.8mAh/g when the cycle was up to 300 th.