CN105742619B - A kind of unformed Mn oxide cladding ferriferous oxide lithium/anode material of lithium-ion battery and preparation method thereof - Google Patents

Abstract

The invention discloses a kind of preparation methods of the unformed compound ferriferous oxide lithium/anode material of lithium-ion battery of Mn oxide, include the following steps：The mixed liquor of potassium permanganate and acid is heated to 20-200 °C, then homodisperse ferriferous oxide solution in deionized water is added dropwise thereto, and 1-48h is kept the temperature at 20-200 °C, the unformed Mn oxide cladding silicon/iron oxide composite material of core-shell structure is obtained after washing centrifugation.The compound ferriferous oxide lithium/anode material of lithium-ion battery conductivity of unformed Mn oxide of core-shell structure prepared by the present invention is good, stable structure, and specific capacity is high, and cycle performance is excellent；In addition, abundant raw material of the present invention, cost economy, preparation method are simple controllable, it can be achieved that large-scale production.

Description

An amorphous manganese oxide-coated iron oxide lithium/sodium ion battery negative electrode material and its preparation method

technical field

The invention belongs to the field of energy materials, and in particular relates to a novel lithium-ion or sodium-ion battery electrode material and a preparation method thereof.

Background technique

With the rapid development of the global economy, energy and environmental issues have become increasingly prominent. The development of new green energy materials has become an extremely urgent task, especially in lithium-ion/sodium-ion battery electrode materials. The traditional negative electrode materials are carbon materials such as graphite, but due to their small specific capacity (372mAh g ^-1 ), it has been difficult to meet the current demand. In recent years, transition metal oxides have attracted more and more attention because of their high theoretical specific capacity (~500-1000mAh g ^-1 ), high energy density, abundant raw materials, low cost and environmental friendliness, especially iron oxide. Fe ₂ O ₃ and Fe ₃ O ₄ are mainly iron oxides currently used as negative electrode materials, and their theoretical specific capacities are 1007mAh g ^-1 and 928mAh g ^-1 , respectively. Although iron oxide has many advantages as an electrode material, the conductivity of iron oxide is low, there is a large volume expansion during charge and discharge, and there is a structural change, and the solid electrolyte interface (SEI) film cannot exist stably, thus Cause capacity attenuation, cycle stability decline. At present, the industry generally believes that surface modification of iron oxide nanostructure materials is an effective method to solve the problem of structural stability, such as carbon-coated iron oxide lithium-ion battery anode materials (typical domestic patent: application number 201410389784.1; typical Literature: Adv.Funct.Mater.2008,18,3941; Adv.Energy Mater.2015,5,1401123). The carbon coating improves the electronic conductivity of the electrode material and also stabilizes the SEI film, improving the cycle performance of the electrode material. However, the preparation of this material requires a high temperature (generally 300-800°C), which makes it difficult to achieve large-scale production and application. In addition, carbon has no lithium storage activity and has a low specific capacity. As an electrode material, manganese oxide also has a high theoretical specific capacity and a low working voltage. Some literature (J.Mater.Chem.A, 2015, 3, 22066) reported that MnO ₂ can be used as a positive electrode material for capacitors after being composited on the surface of Fe ₂ O _3. MnO ₂ can not only effectively resist volume change, but also improve the conductivity of the material. . However, _MnO2 in this material has a crystal form, so there is a certain amount of crystal water, and the existence of water molecules has a certain harmful effect on lithium/sodium ion batteries.

Contents of the invention

The object of the present invention is to provide an economical and effective amorphous manganese oxide-coated iron oxide lithium/sodium ion battery electrode material and a preparation method thereof based on the problems existing in the prior art.

The preparation method of amorphous manganese oxide-coated iron oxide lithium/sodium ion battery negative electrode material comprises the following steps:

(1) Disperse iron oxides in deionized water and ultrasonically uniformly obtain solution A; the concentration of the iron oxides is 0.001-5M; dissolve a certain amount of potassium permanganate in deionized water to obtain potassium permanganate solution, And add a certain amount of acid to obtain solution B; the concentration of the potassium permanganate solution is 0.001-5M, the molar ratio of potassium permanganate to H ⁺ is 0.01-10:1, the volume of the potassium permanganate solution and the acid The ratio is 1-100:1; after heating solution B to 20-200°C, add solution A to solution B dropwise; then keep the mixed solution at 20-200°C for 1-48h under magnetic stirring;

(2) After natural cooling, the product obtained in step (1) was washed and centrifuged several times with deionized water and ethanol, and then dried to obtain a brown powder, which is an amorphous manganese oxide-coated iron oxide with a shell-core structure composite material.

Preferably, the reaction vessel used in step (1) is a well-sealed reaction vessel.

Preferably, the manganese oxide is an amorphous compound of manganese and oxygen.

According to the above method, an amorphous manganese oxide-coated iron oxide lithium/sodium ion battery negative electrode material is prepared.

The purpose of the amorphous manganese oxide coated iron oxide lithium/sodium ion battery negative electrode material prepared according to the above method: the amorphous manganese oxide coated iron oxide composite material or the mixture containing this material is used to make lithium/sodium ion battery Sodium ion battery anode material.

Negative electrode of lithium/sodium ion battery: after adopting the negative electrode material described in claim 5, binder and conductive agent mixed in a solvent to form a slurry, evenly apply it to current collectors such as foamed nickel, foamed copper or copper sheet, and dry After being pressed into a tablet, the lithium/sodium battery negative electrode is obtained.

Lithium/sodium ion battery: The lithium/sodium ion battery is composed of the above-mentioned negative electrode, lithium or sodium as the positive electrode, and a separator and electrolyte in between.

An amorphous manganese oxide-coated manganese oxide lithium/sodium ion battery electrode material and a preparation method thereof of the present invention specifically have the following beneficial effects:

(1) The preparation process of the present invention is simple, the cost is low, and large-scale production and application can be realized.

(2) The amorphous manganese oxide-coated iron oxide composite material with a core-shell structure prepared by the present invention has uniform morphology and structure, and has good electrochemical performance.

(3) The manganese oxide coating layer of the present invention not only improves the electrical conductivity of the material, but also can resist the volume change of the iron oxide during charging and discharging, and improves the kinetic performance of the electrode.

(4) The manganese oxide of the present invention is amorphous, so there is no crystal water and will not cause harm to lithium/sodium ion batteries.

Description of drawings

The specific implementation manners of the present invention will be described in further detail below in conjunction with the accompanying drawings.

Figure 1 is the XRD pattern of Fe ₂ O ₃ and the amorphous MnO ₂ coated Fe ₂ O ₃ composite material (heating time: 8h) prepared in Example 1.

Figure 2 is a 300,000x scanning electron microscope image of Fe ₂ O ₃ .

Fig. 3 is a scanning electron micrograph of the amorphous MnO ₂ coated Fe ₂ O ₃ composite material (heating time: 8 h) prepared in Example 1.

Figure 4 is the scanning electron microscope image of the MnO ₂ coated Fe ₂ O ₃ composite prepared by the closest prior art (J.Mater.Chem.A, 2015, 3, 22066).

Fig. 5 is the cycle performance diagram of the Fe ₂ O ₃ and amorphous MnO ₂ coated Fe ₂ O ₃ composites (heating time: 8h) prepared in Example 1.

Detailed ways

The following are specific implementation cases based on the technical solution of the present invention, and the present invention can be better understood through the following examples. It should be noted that the present invention is not limited to the following embodiments, and many variations are possible. According to the principles of the present invention, non-substantial modifications or changes made to the present invention in terms of form and content by those skilled in the art all belong to the scope of protection of the present invention.

Example 1

Solution A: Weigh 80mg Fe ₂ O ₃ , disperse it in 25mL deionized water, and obtain a uniform dispersion after ultrasonication for 30 minutes. Solution B: Dissolve 0.20g KMnO ₄ in 25mL deionized water, then add 0.8mL 1M HCl, and stir well. After solution B was heated to 95°C, solution A was added dropwise thereto. Under magnetic stirring, the mixture was heated at 95 °C for 2 h. After natural cooling, the product was centrifuged several times with deionized water and ethanol, and then dried at 80°C to obtain a brown amorphous MnO ₂ coated Fe ₂ O ₃ composite.

In the above preparation method, heating the mixed solution at 95° C. for 2 h to extend to 5 h, 8 h, 14 h or 23 h can also obtain a brown amorphous MnO ₂ coated Fe ₂ O ₃ composite material.

Using N-methyl-pyrrolidone (NMP) as solvent, mix the amorphous MnO ₂ coated Fe ₂ O ₃ composite material with acetylene black and polyvinylidene fluoride (PVDF) at a mass ratio of 8:1:1, and spread evenly On the nickel foam, after vacuum drying, it is stamped into a circular electrode sheet, the metal lithium sheet is used as the positive electrode, the electrolyte is 1M LiPF ₆ /DMC/EC (the molar ratio of DMC and EC is 1:1), and the separator is polypropylene microporous Membrane Celgard 2300, assembled into simulated cells.

Carry out charge and discharge tests on the simulated battery. When the heating time is 2h, the current density is 50mA g ^-1 , the voltage range is 0.05-3.0V, and the specific capacity is 335mAh g ^-1 after 50 cycles; when the heating time is 5h , the current density is 100mAg ^-1 , the voltage range is 0.05-3.0V, the specific capacity after 50 cycles is 619mAh g ^-1 ; when the heating time is 8h, the current density is 100mA g ^-1 , the voltage range is 0.05-3.0 V, the specific capacity after 50 cycles is 753 mAh g ^-1 ; when the heating time is 14 hours, the current density is 100 mA g ^-1 , the voltage range is 0.05-3.0 V, and the specific capacity after 50 cycles is 758 mAh g ^-1 ; When the heating time is 23h, the current density is 100mA g ^-1 , the voltage range is 0.05-3.0V, and the specific capacity is 341mAh g ^-1 after 50 cycles.

In particular, when the heating time is 8h, it can be seen from Figure 1 that the diffraction peak position of the MnO ₂ coated Fe ₂ O ₃ composite material is basically the same as that of Fe ₂ O ₃ , indicating that MnO ₂ is amorphous. It can be seen from Figure 2, Figure 3 and Figure 4 that MnO ₂ is very uniformly coated on the surface of Fe ₂ O ₃ . In addition, compared with the closest prior art (J.Mater.Chem.A, 2015, 3, 22066), the MnO ₂ coated Fe ₂ O ₃ composite material with a core-shell structure obtained by heating at 160°C for 24h, this paper In the embodiment, the heating time is shorter and the heating temperature is lower, so the cost is relatively low.

The experimental results show that when the heating time is about 8-14h, the growth of MnO ₂ on Fe ₂ O ₃ is relatively uniform, which is a more suitable time; when the heating time is shorter, MnO ₂ is still growing, and the growth on Fe ₂ O ₃ There is not much MnO ₂ ; when the time is longer, such as 23h, the MnO ₂ on Fe ₂ O ₃ decreases.

The experimental results show that the XRD pattern of 5h, 8h, 14h, and 16h shows that the obtained MnO ₂ is all amorphous.

Example 2

Solution A: Weigh 400mg Fe ₂ O ₃ , disperse it in 25mL deionized water, and obtain a uniform dispersion after ultrasonication for 30 minutes. Solution B: Dissolve 1.20g KMnO ₄ in 25mL deionized water, then add 10.0mL 1M HCl, and stir well. After solution B was heated to 140°C, solution A was added dropwise thereto. Under magnetic stirring, the mixture was heated at 140 °C for 8 h. After natural cooling, the product was centrifuged several times with deionized water and ethanol, and then dried at 80°C to obtain a brown amorphous MnO ₂ coated Fe ₂ O ₃ composite. Under H ₂ (30%H ₂ and 70%Ar) atmosphere, the prepared MnO ₂ coated Fe ₃ O ₄ composite was fired at 350°C for 5h. After cooling to room temperature, the product was centrifugally cleaned, and then dried to obtain an amorphous MnO ₂ coated Fe ₃ O ₄ composite material.

Using N-methyl-pyrrolidone (NMP) as the solvent, mix the amorphous MnO ₂ coated Fe ₃ O ₄ composite with acetylene black and polyvinylidene fluoride (PVDF) at a mass ratio of 8:1:1, and spread evenly On the nickel foam, after vacuum drying, it is stamped into a circular electrode sheet, the metal lithium sheet is used as the positive electrode, the electrolyte is 1M LiPF ₆ /DMC/EC (the molar ratio of DMC and EC is 1:1), and the separator is polypropylene microporous Membrane Celgard 2300, assembled into simulated cells. The charge and discharge test was carried out on the simulated battery, the current density was 100mA g ^-1 , the voltage range was 0.05-3.0V, and the specific capacity was 494mAh g ^-1 after 50 cycles.

Example 3

Under H ₂ (30% H ₂ and 70% Ar) atmosphere, Fe ₂ O ₃ was fired at 350°C for 5 h. After cooling to room temperature, the product was centrifugally washed and dried to obtain Fe ₃ O ₄ . Solution A: Weigh 40mg Fe ₃ O ₄ , disperse it in 25mL deionized water, and obtain a uniform dispersion after ultrasonication for 30 minutes. Solution B: Dissolve 0.40g KMnO ₄ in 25mL deionized water, then add 0.5mL 2M HCl, and stir well. After solution B was heated to 95°C, solution A was added dropwise thereto. Under magnetic stirring, the mixture was heated at 95 °C for 8 h. After natural cooling, the product was centrifuged several times with deionized water and ethanol, and then dried at 80°C to obtain a brown amorphous MnO ₂ coated Fe ₃ O ₄ composite.

Using N-methyl-pyrrolidone (NMP) as a solvent, mix MnO ₂ coated Fe ₃ O ₄ composite material with acetylene black and polyvinylidene fluoride (PVDF) at a mass ratio of 8:1:1, and evenly coat the foam On nickel, after vacuum drying, it is stamped into a circular electrode sheet, the metal lithium sheet is used as the positive electrode, the electrolyte is 1M LiPF ₆ /DMC/EC (the molar ratio of DMC and EC is 1:1), and the separator is polypropylene microporous membrane Celgard 2300, assembled into a simulated battery. The charge-discharge test was carried out on the simulated battery, the current density was 100mA g ^-1 , the voltage range was 0.05-3.0V, and the specific capacity was 714 mAh g ^-1 after 50 cycles.

Claims (7)

1. a kind of preparation method of unformed Mn oxide cladding ferriferous oxide lithium/anode material of lithium-ion battery, feature exist In including the following steps：

(1) by ferriferous oxide dispersion in deionized water, ultrasound uniformly, obtains solution A；A concentration of 0.001- of ferriferous oxide 5M；A certain amount of potassium permanganate is dissolved in deionized water and obtains liquor potassic permanganate, and adds in a certain amount of acid, obtains solution B；The liquor potassic permanganate concentration is 0.001-5M, potassium permanganate and H⁺Molar ratio is 0.01-10：1, liquor potassic permanganate Volume ratio with acid is 1-100：1；After solution B is heated to 20-200 DEG C, solution A is added in into solution B dropwise；Then in magnetic Mixed solution is kept the temperature into 1-48h at 20-200 DEG C under power stirring；

(2) after natural cooling, the product deionized water and ethyl alcohol that are obtained in step (1) is cleaned into centrifugation for several times, then dried It is dry to obtain the unformed Mn oxide cladding silicon/iron oxide composite material of brown ceramic powder, i.e. core-shell structure.

2. preparation method according to claim 1, it is characterised in that：The reaction vessel used in step (1) is leakproofness Good reaction vessel.

3. preparation method according to claim 1, it is characterised in that：The Mn oxide is manganese and the amorphous state chemical combination of oxygen Object.

4. unformed Mn oxide cladding ferriferous oxide lithium/sodium is prepared according to any one of claim 1-3 the methods Ion battery cathode material.

5. according to unformed Mn oxide cladding ferriferous oxide lithium/sodium prepared by any one of claim 1-3 the methods from The purposes of sub- cell negative electrode material, it is characterised in that：Unformed Mn oxide cladding silicon/iron oxide composite material contains this The mixture of kind material is used to make lithium/anode material of lithium-ion battery.

6. lithium/sodium-ion battery cathode, it is characterised in that：Using the negative material described in claim 5 and binding agent, conductive agent Even to be coated onto on the collectors such as nickel foam, foam copper or copper sheet after being mixed to form slurry in a solvent, drying obtains after being pressed into piece Lithium/sode cell cathode.

7. lithium/sodium-ion battery, it is characterised in that：Using the cathode described in claim 6, lithium or sodium are as anode, Yi Jijie In diaphragm between the two and electrolyte composition lithium/sodium-ion battery.