阅读说明：本技术 一种MnO/C复合材料及其制备方法和将其作为锂离子电池负极材料的应用 (MnO/C composite material, preparation method thereof and application of MnO/C composite material as lithium ion battery negative electrode material ) 是由 吴正颖 林艳 陈志刚 刘谢 查振龙 钱君超 于 2019-09-19 设计创作，主要内容包括：本发明公开了一种具有优良电化学性能的MnO/C复合材料,其微观形貌呈现C层-MnO颗粒-C层的三明治夹层结构,而这种复合材料的制备方法,其步骤为：1)将山茶花花瓣用去离子水洗涤若干次；2)将洗涤后的花瓣置于乙醇溶液中浸泡2~4周,以除去花瓣中的色素和其他有机物质；3)将浸泡后的花瓣用去离子水洗净,在空气中滤干；4)将滤干的花瓣浸入配制好的锰源浓度<I>C</I><Sub>Mn(The invention discloses a MnO/C composite material with excellent electrochemical performance, the microstructure of which presents a sandwich structure of a C layer-MnO particles-C layer, and the preparation method of the composite material comprises the steps of 1) washing camellia petals with deionized water for a plurality of times, 2) soaking the washed petals in an ethanol solution for 2 ~ 4 weeks to remove pigments and other organic substances in the petals, 3) washing the soaked petals with deionized water, draining in the air, and 4) soaking the drained petals in a prepared manganese source with a concentration C Mn =0.05～0.1 mol L ‑1 Soaking in the manganese acetate aqueous solution for 48 ~ 96 hours, washing with deionized water, naturally drying in the air to obtain dried petals, and 5) calcining at 600 ℃ of ~ 800 ℃ in nitrogen atmosphere to obtain a composite material.)

1. The MnO/C composite material is characterized in that the microstructure of the MnO/C composite material is a sandwich structure of a C layer, MnO particles and a C layer.

2. The MnO/C composite as claimed in claim 1, wherein: the diameter of MnO particles is 20-40 nm.

3. The MnO/C composite as claimed in claim 1, wherein: when the material is used as a lithium ion battery cathode material, after 300 cycles, the electrode is reversibleThe specific capacity reaches and is stabilized at 445 to 563mAhg^-1The coulomb efficiency was 99%.

4. A method of making a composite material according to any one of claims 1 ~ 3, comprising the steps of:

1) washing camellia petals with deionized water for several times;

2) soaking the camellia petals washed in the step 1) in an ethanol solution for 2 ~ 4 weeks to remove pigments and other organic substances in the petals;

3) cleaning the petals soaked in the ethanol solution in the step 2) with deionized water, and filtering the petals in the air;

4) immersing the petals drained in the step 3) into the prepared manganese source concentrationC _Mn = 0.05～0.1 mol L^-1Soaking in the manganese acetate aqueous solution for n hours until n =48 ~ 96, washing with deionized water, and naturally drying in the air to obtain dried petals;

5) calcining the dried petals obtained in the step 4) at the temperature of 600 ℃ and ~ 800 ℃ in a nitrogen atmosphere to obtain the required MnO/C composite material.

5. The method according to claim 4, wherein the ethanol solution of step 2) has a volume ratio V of ethanol to water_EtOH/V_H2O= 1:1 ~ 4: 4, and the acidity of the ethanol solution was adjusted to pH = 2 ~ 3 by hydrochloric acid.

6. Process according to claim 5, characterized in that the volume ratio V of ethanol to water_EtOH/V_H2O= 1:1, said pH = 2.

7. The method according to claim 4, wherein the calcination temperature in the step 5) is 800 ℃.

8. The method according to claim 4, wherein the manganese source is used in the step 5) at a concentration ofC _Mn = 0.1 mol L^-1。

9. The method according to claim 4, wherein n = 72.

10. Use of the composite material of any one of claims 1 ~ 3 as a negative electrode material for a lithium ion battery.

Technical Field

The invention relates to a MnO/C composite material, a preparation method thereof and application of the MnO/C composite material as a lithium ion battery cathode material.

Background

The material has high theoretical capacity (756 mAhg)^-1) Low voltage hysteresis (<0.8V), low switching potential (1.032V Vs Li/Li)⁺) The advantage of (1). Meanwhile, MnO becomes a good candidate material for a high-performance lithium ion battery due to the advantages of relative cheapness, rich properties, environmental protection and the like. However, pure MnO materials have problems such as inherent low conductivity and structural collapse due to lattice shrinkage during lithium ion deintercalation. Therefore, carbonaceous materials are generally used as a matrix for transition metal oxides to alleviate the above-mentioned drawbacks because they have high electrical conductivity and elasticity. Some MnO/carbon composites have been reported as lithium battery negative electrode materials, such as MnO/carbon fibers, MnO @ C hollow nanospheres, porous MnO @ C nanocomposites and MnO/carbon core shell nanorods. The above results indicate that the electrical properties of carbon-based materials depend largely on their size and structure. For example, the RGO-MnO-RGO sandwich nano-structured material synthesized by Yuan et al shows excellent performance when being used as a negative electrode material of a lithium battery. The unique layered structure provides excellent support and protection for volume changes, resulting in structural strain and improved lithium storage capability of the electrode. However, most of these synthetic methods are relatively complicated, and simpler and more direct methods are required for preparing the MnO/C layered nanocomposite.

The biomateplate method has been widely used to prepare transition metal oxide materials. Natural biomaterials can provide a variety of architectures with complex morphologies and specialized functions. Especially plant leaves, are often used to make layered structure materials due to their unique natural cellular structure. For example, Yang et al synthesized Co by using rose petals as a biological template₃O₄The sample, which exhibits a specific nanosheet morphology, with a thickness similar to the original petals. Compared with an artificial template, the biological material has the advantages of low cost, reproducibility, easy removal and the like. This motivated us to use petals as templates to prepare the structure of MnO particles grown in the carbon layer by using their natural lamellar structure.

Disclosure of Invention

The invention aims to: provides a new MnO/C composite material with a special structure and a preparation method thereof, and the MnO/C composite material can be used as an electrode material of a lithium ion battery to show good lithium storage performance.

In order to solve the technical problems, the technical scheme of the invention is as follows: the MnO/C composite material is characterized in that the microstructure of the MnO/C composite material is a sandwich structure of a C layer, MnO particles and a C layer.

Further, the MnO particles of the present invention have a diameter of 20 to 40 nm.

Furthermore, when the MnO/C composite material is used as a lithium ion battery cathode material, the reversible specific capacity of the electrode reaches and is stabilized at 445-563 mAhg after 300 cycles^-1The coulomb efficiency was 99%.

The invention also provides a preparation method of the composite material, which is characterized by comprising the following steps:

1) washing camellia petals with deionized water for several times;

2) soaking the camellia petals washed in the step 1) in an ethanol solution for 2 ~ 4 weeks to remove pigments and other organic substances in the petals;

3) cleaning the petals soaked in the ethanol solution in the step 2) with deionized water, and filtering the petals in the air;

4) the petals filtered and dried in the step 3)Immersing in the prepared manganese source concentrationC _Mn = 0.05～0.1 mol L^-1The method comprises the steps of soaking the petals in a manganese acetate aqueous solution for n hours, washing the petals with deionized water with n =48 ~ 96, and naturally airing the petals in the air to obtain dried petals, wherein the filtration of the previous step is different from the airing of the previous step, the filtration refers to the filtration of the deionized water on the surfaces of the petals by using a common string bag or a common sieve, and the airing refers to the state that the petals are required to be dehydrated under the natural state.

5) Calcining the dried petals obtained in the step 4) at the temperature of 600 ℃ and ~ 800 ℃ in a nitrogen atmosphere to obtain the required MnO/C composite material.

Further, in the ethanol solution of step 2) of the present invention, the volume ratio V of ethanol to water_EtOH/V_H2O= 1:1 ~ 4: 4, and the acidity of the ethanol solution was adjusted to pH = 2 ~ 3 by hydrochloric acid.

Further, the volume ratio V of the ethanol to the water is_EtOH/V_H2O= 1:1, said pH = 2.

Further, the calcination temperature in step 5) of the present invention is 800 ℃.

Further, the concentration of the manganese source in the step 5) of the invention isC _Mn = 0.1 mol L^-1。

An application of the MnO/C composite material as a lithium ion battery cathode material.

In this work, a new type of MnO/C nanomaterials was designed and prepared by uniformly embedding MnO particles ranging in size from about 20 to 40nm in diameter into a carbon layer to form a special "layer-particle-layer" sandwich structure. Accordingly, the synthesized nanocomposite shows good lithium storage performance as a negative electrode material of a lithium ion battery. And the influence of the concentration and the calcination temperature on the material performance is researched.

Compared with the prior art, the invention has the following advantages:

1. the MnO/C composite material is successfully synthesized by taking camellia petals as a biological template through the processes of infiltration, calcination and the like, and when the material is used as a negative electrode material of a lithium ion battery, the MnO/C composite material is prepared byAfter 300 times of circulation, the reversible specific capacity of the electrode reaches and is stabilized at 445 to 563mAhg^-1The coulomb efficiency was 99%.

2. The morphology structure and the composition of the material are respectively analyzed by SEM and TEM, and the obtained composite material not only replicates the micro morphology of petals, but also presents a special sandwich structure of C/MnO/C, namely 'layer-particle-layer', and the size of MnO nano particles in the composite material is 20-40 nm.

3. The MnO/C composite material has better electrochemical performance.

When the calcining temperature is constant, the concentration of the manganese source is 0.1 mol L^-1The obtained composite material has better electrochemical performance, and the MnO/C (0.1) -800 material reaches 563mA h g after 300 cycles^-1The reversible specific capacity of the material is determined under the same condition (469 mA h g) compared with MnO/C (0.05) -800 material^-1) High. The MnO concentration in the material is high, so that the material can exert the characteristics of manganese oxide, and the electrochemical performance of the material is improved.

When the concentration is constant, the composite material obtained at a calcination temperature of 800 ℃ (MnO/C (0.1) -800) has better electrochemical performance than the composite material obtained at a calcination temperature of 600 ℃ (MnO/C (0.1) -600), and after 300 cycles, two samples respectively reach 563mAhg^-1And 449 mAh g^-1The reversible specific capacity of (a). This is because the higher the temperature, the higher the crystallinity of the template-derived carbon contained in the material, which is favorable for ion conduction, and the higher the electrode cycling performance of the material.

Drawings

The invention is further described with reference to the following figures and examples.

FIG. 1 is an SEM image of a MnO/C composite material (MnO/C (0.1) -600 samples) prepared according to the present invention;

FIGS. 2 to 3 are TEM images (resolution increased step by step) of MnO/C composites (MnO/C (0.1) -600 samples) prepared according to the present invention;

FIG. 4 is a TEM image of a MnO/C composite material prepared according to the present invention (MnO/C (0.1) -800 sample);

FIG. 5 is a schematic diagram of the mechanism of formation of a MnO/C composite of the present invention;

FIG. 6 is a graph of MnO/C (0.05) -600 samples, MnO/C (0.1) -600 samples, MnO/C (0.05) -800 samples, MnO/C (0.1) -800 samples, MnO samples and biochar at a current density of 100 mAg^-1Comparative graph of cycle performance of the following.

Detailed Description