CN111554893A - A kind of preparation method of lithium battery anode material molybdenum oxide composite - Google Patents

Abstract

The invention discloses a preparation method of a lithium battery negative electrode material molybdenum oxide composite material. The invention successfully synthesizes a molybdenum oxide composite material through a hydrothermal reaction and a sintering reduction reaction. The composite synthesized by the present invention is used as a negative electrode material for a lithium battery, and at a current density of 200 mA g ^-1 , the first discharge specific capacity is 1113 mA hg ^-1 , and the discharge specific capacity remains above 395 mA hg ^-1 after 100 charge-discharge cycles, Coulombic efficiency can be maintained above 98%. In the whole preparation process, the synthesis method is simple, easy to operate, low in preparation cost, low in equipment investment, and suitable for mass production.

Description

A kind of preparation method of lithium battery anode material molybdenum oxide composite

technical field

The invention belongs to the field of material chemistry, and in particular relates to a preparation method of a molybdenum oxide compound as a negative electrode material of a lithium battery.

Background technique

Lithium-ion batteries are widely used in electric vehicles, portable electronic devices, and grid energy storage due to their very high energy density and power density. Since Sony successfully commercialized lithium-ion batteries in 1991, the power density of lithium-ion batteries has steadily increased through continuous exploration by researchers. The level of lithium-ion battery capacity is one of the important indicators to measure lithium-ion batteries. As a part of lithium ion battery, the electrochemical performance of negative electrode material directly affects the performance of lithium ion battery. At present, graphite is used as a negative electrode material for commercial lithium-ion batteries, and its theoretical specific capacity is 372mAh/g, and the specific capacity of commercial batteries can reach 330-340mAh/g. Low specific capacity has gradually been unable to meet the needs of modern society for high energy storage devices. Moreover, during the charging and discharging process, the graphite layer collapses due to the decomposition of the electrolyte and the intercalation of solvent molecules between the graphite layers, which leads to the rapid decay of the battery capacity and greatly reduces the battery cycle life. Relatively speaking, transition metal oxides have very high capacities (about twice that of graphite) and are candidates for anode materials for next-generation lithium-ion batteries. There are many kinds of molybdenum oxides, including MoO ₂ , MoO ₃ , Mo ₄ O ₁₁ and so on. Among them, the theoretical specific capacity of MoO ₂ is as high as 838mAh g ^-1 , and the conductivity is 8.8× ^10-5 Ω·cm. During the discharge process, each Mo in the Mo ₄ O ₁₁ compound can intercalate 2.12 lithium atoms with excellent electrochemical performance. However, some oxides have poor cycle performance, and their applications are greatly limited.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a method for preparing a lithium battery negative electrode material molybdenum oxide composite, the chemical formula of the composite is MoO ₂ ·Mo ₄ O ₁₁ or MoO ₂ /Mo ₄ O ₁₁ .

The technical solution adopted by the present invention to solve the above technical problems is: a preparation method of a lithium battery negative electrode material molybdenum oxide composite, the lithium battery negative electrode material is prepared by a combination method of hydrothermal reaction and high temperature sintering technology, and specifically includes: The following steps:

(1) take by weighing the ammonium heptamolybdate and 2-aminopyridine that an appropriate mass ratio is 1:1, ultrasonically 30 minutes in the mixed solvent of water and ethanol, obtain mixture solution; Wherein, the volume ratio of water and ethanol is 1 :1;

(2) above-mentioned mixture solution is transferred to the stainless steel reactor with polytetrafluoroethylene lining, placed in blast drying oven, temperature 150～180 ℃ of reaction 24～48 hours, remove solvent, filter, naturally air dry, get the reaction product;

(3) The product obtained above is put into a tube furnace, calcined at 500-700° C. for 4 hours under nitrogen atmosphere, and after natural cooling, a molybdenum oxide compound is obtained, abbreviated as MoO ₂ ·Mo ₄ O ₁₁ or MoO ₂ /Mo ₄ O ₁₁ ;

The surface of the molybdenum oxide composite is covered with a layer of carbon, and the mass content of the carbon is 0.5-1.0%;

The chemical formula of the ammonium heptamolybdate is (NH ₄ ) ₆ Mo ₇ O ₂₄ ;

Said solvent and synthetic raw materials are all chemically pure.

The above-mentioned MoO ₂ ·Mo ₄ O ₁₁ composite was used as the negative electrode material for lithium batteries. At a current density of 200 mA g ^-1 , the first discharge specific capacity was 1113 mAh g ^-1 , and the discharge specific capacity remained at 395 mA hg after 100 charge-discharge cycles. Above ^-1 , the Coulombic efficiency can be maintained above 98%.

Compared with the prior art, the molybdenum oxide composite material prepared by the present invention has the following characteristics:

The surface of the molybdenum oxide composite prepared by the invention is coated with a layer of carbon, and the carbon content is 0.5-1.0%, which is beneficial to improve the electrical conductivity and reversible capacity of the material; in the reaction, part of the molybdenum with oxidation number of +6 is reduced to Molybdenum with oxidation numbers of +5 and +4 forms a molybdenum oxide complex MoO ₂ ·Mo ₄ O ₁₁ with a specific composition; the prepared molybdenum oxide complex is used as a negative electrode material for lithium ion batteries, and the current density is 200m Ag ^-1 The first discharge specific capacity was 1113 mA hg ^-1 , the discharge specific capacity remained above 395 mA hg ^-1 after 100 charge-discharge cycles, and the Coulombic efficiency could be maintained above 98%.

Description of drawings

Fig. 1 is the XRD pattern of the MoO ₂ /Mo ₄ O ₁₁ composite material prepared by the present invention;

Fig. 2 is the SEM image of the MoO ₂ /Mo ₄ O ₁₁ composite material prepared by the present invention;

FIG. 3 is a charge-discharge cycle diagram of the MoO ₂ /Mo ₄ O ₁₁ composite prepared by the present invention as a negative electrode material for a lithium battery.

Detailed ways

The present invention will be specifically described below with reference to the embodiments.

Example 1:

Weigh 1.0 g of ammonium heptamolybdate and 1.0 g of 2-aminopyridine, sonicate in 10 mL of water and 10 mL of ethanol mixed solvent for 30 minutes to obtain a mixture solution; transfer the above mixture solution to 25 mL of stainless steel lined with polytetrafluoroethylene for reaction In the kettle, placed in a blast drying oven, reacted at a temperature of 180 ° C for 24 hours, removed the solvent, filtered, and naturally air-dried to obtain the reaction product; put the product obtained above into a tube furnace, and calcined at 700 ° C under nitrogen atmosphere After 4 hours of natural cooling, a molybdenum oxide composite was obtained, and the chemical formula was abbreviated as MoO ₂ ·Mo ₄ O ₁₁ ; the mass percentage of carbon in the molybdenum oxide composite prepared by elemental analysis was 0.5%; powder diffraction X-ray diffraction The composition of the molybdenum oxide composite prepared by analysis (XRD) was MoO ₂ ·Mo ₄ O ₁₁ (Fig. 1); the morphology of the prepared composite material was observed by scanning electron microscope (SEM) as block (Fig. 2); The as-prepared composite was used as a negative electrode material for lithium batteries. At a current density of 200 mA g ^-1 , the first discharge specific capacity was 1113 mA hg ^-1 , and the discharge specific capacity remained above 395 mA hg ^-1 after 100 charge-discharge cycles. remained above 98% (Figure 3).

Example 2:

Weigh 1.0 g of ammonium heptamolybdate and 1.0 g of 2-aminopyridine, sonicate in 10 mL of water and 10 mL of ethanol mixed solvent for 30 minutes to obtain a mixture solution; transfer the above mixture solution to 25 mL of stainless steel lined with polytetrafluoroethylene for reaction In the kettle, place it in a blast drying oven, react at a temperature of 150 ° C for 48 hours, remove the solvent, filter, and naturally air dry to obtain the reaction product; put the above-obtained product into a tube furnace, and calcine at 500 ° C under a nitrogen atmosphere After 4 hours of natural cooling, a molybdenum oxide composite was obtained, and the chemical formula was abbreviated as MoO ₂ ·Mo ₄ O ₁₁ ; the mass percentage of carbon in the molybdenum oxide composite prepared by elemental analysis was 1.0%; powder diffraction X-ray diffraction The composition of the prepared molybdenum oxide composite was analyzed; the morphology of the prepared composite material was observed by SEM; the electrochemical performance of the prepared composite was tested as a lithium battery anode material.

Example 3:

Weigh 1.0 g of ammonium heptamolybdate and 1.0 g of 2-aminopyridine, sonicate in 10 mL of water and 10 mL of ethanol mixed solvent for 30 minutes to obtain a mixture solution; transfer the above mixture solution to 25 mL of stainless steel lined with polytetrafluoroethylene for reaction In the kettle, put it in a blast drying oven, react at a temperature of 160 ° C for 36 hours, remove the solvent, filter, and naturally air dry to obtain a reaction product; put the product obtained above into a tube furnace, and calcine at 600 ° C under a nitrogen atmosphere After 4 hours of natural cooling, a molybdenum oxide composite was obtained, and the chemical formula was abbreviated as MoO ₂ ·Mo ₄ O ₁₁ ; the mass percentage of carbon in the molybdenum oxide composite prepared by elemental analysis was 0.7%; powder diffraction X-ray diffraction The composition of the prepared molybdenum oxide composite was analyzed; the morphology of the prepared composite material was observed by SEM; the electrochemical performance of the prepared composite was tested as a lithium battery anode material.

Claims (2)

1. a preparation method of lithium battery negative electrode material molybdenum oxide composite, is characterized in that, described preparation method comprises the following steps: (1) take by weighing the ammonium heptamolybdate and 2-aminopyridine that an appropriate mass ratio is 1:1, ultrasonically 30 minutes in the mixed solvent of water and ethanol, obtain mixture solution; Wherein, the volume ratio of water and ethanol is 1 :1; (2) above-mentioned mixture solution is transferred to the stainless steel reactor with polytetrafluoroethylene lining, placed in blast drying oven, temperature 150～180 ℃ of reaction 24～48 hours, remove solvent, filter, naturally air dry, get the reaction product; (3) putting the product obtained above into a tube furnace, calcining at 500-700° C. for 4 hours under nitrogen atmosphere, and after natural cooling, a molybdenum oxide composite is obtained, abbreviated as MoO ₂ ·Mo ₄ O ₁₁ ; The surface of the molybdenum oxide composite is covered with a layer of carbon, and the mass content of the carbon is 0.5-1.0%; The chemical formula of the ammonium heptamolybdate is (NH ₄ ) ₆ Mo ₇ O ₂₄ ; Said solvent and synthetic raw materials are all chemically pure. 2. the molybdenum oxide composite that a preparation method as claimed in claim 1 obtains is as lithium ion battery negative electrode material, it is characterized in that, under 200m A g ^-1 current density, first discharge specific capacity is 1113mA hg ^-1 , After 100 charge-discharge cycles, the discharge specific capacity remains above 395 mA hg ^-1 , and the Coulombic efficiency can be maintained above 98%.

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