CN111285408A - A method for preparing iron oxide negative electrode material for lithium ion power battery - Google Patents

Abstract

The invention discloses a method for preparing an iron oxide cathode material for a lithium ion power battery, and relates to the technical field of preparation of electrode materials of lithium ion batteries; the method is based on a sol-gel method, adopts the precursor raw materials of nano iron oxide, glycol, butyl titanate and other materials, and adopts proper temperature, time and component control to realize the long cycle life and high specific capacity of the iron oxide cathode; the reactions involved are: (1) fe is prepared by taking nano iron oxide as a template, butyl titanate as a precursor and citric acid as a chelating agent₂O₃@TiO₂，TiO₂Can be used as a buffer material in the electrode to inhibit the volume expansion of the ferric oxide; (2) the strong reducibility of sodium borohydride is utilized to reduce the composite material under the argon atmosphere to increase oxygen vacancy and increase the conductivity of the material. The invention has simple raw materials and easy realization of the process, and the obtained electrode material keeps high capacity level in long circulation.

Description

A method for preparing iron oxide negative electrode material for lithium ion power battery

technical field

The invention relates to the technical field of preparation of lithium-ion battery electrode materials, in particular to a method for preparing an iron oxide negative electrode material for lithium-ion power batteries.

Background technique

With the continuous innovation and development of science and technology, new energy sources have overcome traditional chemical energy sources that are easy to cause pollution by virtue of the advantages of green, pollution-free, cheap and easy to obtain. Clear waters and lush mountains are invaluable assets. The development of new energy has become the trend of the times and is the top priority in energy development. Lithium batteries are favored in new energy sources, and are widely used in small electrical equipment such as watches, mobile phones, and digital cameras. At the same time, lithium batteries are used in electric vehicles, ships, electric bicycles, aviation aircraft and other transportation networks. also indispensable.

The negative electrode material of lithium battery is one of the key factors determining the electrochemical performance of lithium battery. Lithium-ion battery anode materials are usually divided into three categories: (1) carbon materials, such as natural graphite, graphene, carbon fiber, etc.; (2) oxide materials, such as iron oxide, ferric oxide, silicon oxide; ( 3) Alloy materials, such as magnesium-based alloys, aluminum-based alloys, silicon-based alloys, etc. The currently commercialized graphene cannot meet the increasing demand for high energy due to its low theoretical capacity (372mAh*g ^-1 ), and iron oxide stands out with its high theoretical capacity (1007mAh*g ^-1 ). Fe ₂ O ₃ has the advantages of natural abundance, high electrical conductivity, low cost, and high performance, but due to its large volume expansion and low electrical conductivity during charging and discharging, it leads to low initial Coulombic efficiency and rapid capacity cycling decline.

SUMMARY OF THE INVENTION

In order to overcome the deficiencies of the prior art, the present invention provides a method for preparing an iron oxide negative electrode material for a lithium ion power battery. The raw materials are simple, the process is easy to realize, and the obtained electrode material maintains a high capacity level in a long cycle, and is an iron oxide negative electrode. commercialization provides a possible path.

To achieve the above purpose, the present invention is achieved through the following technical solutions:

A method for preparing an iron oxide negative electrode material for a lithium ion power battery, comprising the following steps:

(1) Add nano-Fe ₂ O ₃ into the mixed solution of distilled water and ethylene glycol, dropwise add butyl titanate and mix and place in the crucible; stir at room temperature, after it is completely dissolved, add citric acid, continue to stir until it is completely dissolved Then, add concentrated ammonia water dropwise to adjust the pH of the solution to 6, and continue stirring for 2.5-3.5 hours at a temperature of 100 °C; stop stirring when a sol appears, and place it in a 100 °C oven to dry overnight; after drying, place it at 490-535 °C calcined in muffle furnace for 2.5-4h, the heating rate is 0.8-1.3℃/min;

(2) adding sodium borohydride to the product obtained in step (1), grinding and mixing in an agate mortar, transferring to a quartz boat, and placing it in a tubular furnace for calcination under argon atmosphere for 55-70min at a temperature of 340- 365 ℃, the heating rate is 1.5-2.2 ℃/min; after calcination, rinse and filter with distilled water for 3 times, and after drying, the negative electrode material Fe ₂ O ₃ @TiO ₂ is obtained.

Preferably, in the step (1), the addition amount of Fe ₂ O ₃ is 3.2g, the addition amount of distilled water is 30ml, the addition amount of ethylene glycol is 30mL, and the addition amount of citric acid is 10g; The added amount is 0.25-1.8ml. Further preferably, the addition amount of the butyl titanate is 0.358ml-1.201ml.

Preferably, in the step (2), the amount of sodium borohydride added is 0.03-0.15 g. Further preferably, the addition amount of sodium borohydride is 0.03158-0.1057g.

Preferably, in the step (1), after drying, it is calcined in a 500°C muffle furnace for 3 hours, and the heating rate of the muffle furnace is 1°C/min.

Preferably, in the step (2), the tube furnace is placed in a tube furnace for calcination under an argon atmosphere for 1 hour, the temperature is 350°C, and the heating rate is 2°C/min.

Compared with the prior art, the present invention has the following technical effects:

(1) the method provided by the present invention is based on sol-gel method and atmosphere protection calcination, and the raw materials used are common chemicals such as commercial micron-level iron oxide, butyl titanate and ethylene glycol, and the raw materials are easy to obtain inexpensive.

(2) When preparing the negative electrode material Fe ₂ O ₃ @TiO ₂ , using sodium borohydride as a reducing agent to reduce the composite material and increase the surface oxygen vacancy is of great help to improve the performance of the material.

(3) The negative electrode material Fe ₂ O ₃ @TiO ₂ in the present invention is a core-shell structure formed by coating iron oxide with titanium dioxide, which effectively inhibits the volume expansion of iron oxide; the iron oxide negative electrode material has high capacity and high stability.

(4) There is no acid washing, no poison, irritating odor and other organic solvents and gases in the synthesis and emissions, which is conducive to the protection of the environment in industrial production.

Description of drawings

1 is a scanning electron microscope image of the commercial pure iron oxide used in Example 1 of the present invention.

2 is a scanning electron microscope image of Fe ₂ O ₃ @0.2TiO ₂ obtained in Example 1 of the present invention.

FIG. 3 is a graph of battery cycle life of Fe ₂ O ₃ @TiO ₂ obtained in Examples 1-3 of the present invention.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the present invention. examples, but not all examples. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1:

1) Preparation of Fe ₂ O ₃ @0.2TiO ₂

Weigh 3.2g of nano Fe ₂ O ₃ into a crucible, add 30mL of distilled water and 30mL of ethylene glycol to mix, take 0.756ml of butyl titanate, and drop it into the crucible. The crucible was placed on a magnetic stirrer and stirred at room temperature. After it was completely dissolved, 10 g of citric acid was weighed and added to the mixed solution, and the stirring was continued for 30 minutes. After it was completely dissolved, concentrated ammonia water was added dropwise to adjust the pH of the solution to 6. Then it was heated to 100°C, and stirring was continued for 3h at a temperature of 100°C. After the sol appeared, the stirring was stopped to obtain a brown wet gel, which was immediately placed in a 100° C. oven to dry overnight. After drying, a brown xerogel was obtained, and the xerogel was calcined in a muffle furnace at 500°C for 3 hours, with a heating rate of 1°C/min, and then cooled to room temperature with a cooling rate of 5°C/min to obtain Fe ₂ O ₃ @ _0.2TiO2 composite.

2) Reduction of Fe ₂ O ₃ @0.2TiO ₂

Weigh 0.06656g of sodium borohydride into an agate mortar, add the sample obtained in step 1), grind and mix, and grind for 30h in a glass room with a water content of about 20%. Transferred to a quartz boat, placed in a tube furnace and calcined in an argon atmosphere for 1 hour at a temperature of 350 °C, a heating rate of 2 °C/min, and then cooled to room temperature with a cooling rate of 5 °C/min. After calcination, a black sample was obtained, and the black sample was placed in a long-necked funnel, rinsed and filtered with distilled water three times. After filtration, the samples were dried at 45°C to obtain the reduced sample Fe ₂ O ₃ @0.2TiO ₂ .

The scanning electron microscope image of the commercial pure iron oxide used in this example is shown in FIG. 1 . It can be seen from Figure 1 that the shape of commercial pure iron oxide is irregular, and the particle size is basically between 0.7-0.8um. The scanning electron microscope image of Fe ₂ O ₃ @0.2TiO ₂ prepared in step 2) of this example is shown in FIG. 2 . It can be seen from Figure 2 that the iron oxide is coated by the sol-gel method to form a block, and the small _TiO2 particles are densely gathered in the outer layer of the iron oxide, and the coating of the iron oxide can effectively inhibit the bulk of the silicon material. The problem of cycle life degradation caused by expansion.

3) Electrode sheet preparation

The prepared composite material Fe ₂ O ₃ @0.2TiO ₂ was used as the negative electrode active material of the battery, and was fully ground with an agate mortar for 20 min, and mixed with conductive agent acetylene black and aqueous binder (2% sodium alginate solution ) according to the mass ratio of 8:1:1, with ultrapure water as solvent and absolute ethanol as auxiliary solvent, fully mixed and adjusted to a slurry with suitable viscosity; The slurry was evenly coated on the current collector on the copper foil; the coated electrode was placed in a 60°C oven, dried at 60°C for 6 hours, taken out and pressed with a powder tablet machine, with a gauge pressure of 10MPa, In order to ensure that the prepared composite negative electrode material, acetylene black and binder can be flatly coated on the clean copper foil; use the punching machine to process the above-mentioned compacted pole piece into an electrode piece, which should be placed in a vacuum oven before use. Dry at 120°C for 12h. After the end, the samples were weighed, put into a sample bag, and transferred to a glove box in an argon atmosphere for later use.

4) Half cell assembly

The battery was assembled in an argon-filled glove box. The separator was polypropylene film, the electrolyte was LiPF6+EC/DMC/EMC with a concentration of 1 mol/L (volume ratio was 1:1:1), and the lithium metal sheet was used as the negative electrode. The finished model is CR2025 button battery.

5) Half cell test

In the first half of the test, the battery needs to be left for 24 hours.

The equipment used in the present invention is a NEWARE-BTS-5V/10mA battery test system, the voltage test range is 0.01-2.5V, and the current density of the cycle life is 100mA/g. The rate performance test current density is 25, 50, 100, 200, 400, 800, 400, 200, 100, 50, 25 mA/g. The performance test results are shown in Table 1 and Figure 3.

Example 2:

The preparation and tableting process of the precursor powder is the same as that of Example 1, except that the amount of butyl titanate added in step 2) is 0.358 ml, and the amount of sodium borohydride used for reduction is 0.03158 g. The sample Fe ₂ O ₃ @0.1TiO ₂ was prepared. The performance test method is the same as that in Example 1, and the performance test results are shown in Table 1 and Figure 3.

Example 3:

The preparation and tableting process of the precursor powder was the same as that of Example 1, except that the amount of butyl titanate added in step 2) was 1.201 ml, and the amount of sodium borohydride used for reduction was 0.1057 g. The sample Fe ₂ O ₃ @0.3TiO ₂ was prepared. The performance test method is the same as that in Example 1, and the performance test results are shown in Table 1 and Figure 3.

Table 1 Electrochemical performance test

As can be seen from FIG. 3 of the present invention, after the iron oxide is coated by the sol-gel method, the cycle life performance of the battery is greatly improved. After 100 cycles at a current of 100 mA, the discharge specific capacity can still maintain 457.536 mAh/g, while that of pure iron oxide is only 35.431 mAh/g.

The above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The recorded technical solutions are modified, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (7)

1. a method for preparing lithium ion power battery iron oxide negative electrode material, is characterized in that, comprises the steps: (1) Add nano-Fe ₂ O ₃ into the mixed solution of distilled water and ethylene glycol, dropwise add butyl titanate and mix and place in the crucible; stir at room temperature, after it is completely dissolved, add citric acid, continue to stir until it is completely dissolved Then, add concentrated ammonia water dropwise to adjust the pH of the solution to 6, and continue stirring for 2.5-3.5 hours at a temperature of 100 °C; stop stirring when a sol appears, and place it in a 100 °C oven to dry overnight; after drying, place it at 490-535 °C calcined in muffle furnace for 2.5-4h, the heating rate is 0.8-1.3℃/min; (2) adding sodium borohydride to the product obtained in step (1), grinding and mixing in an agate mortar, transferring to a quartz boat, and placing it in a tubular furnace for calcination under argon atmosphere for 55-70min at a temperature of 340- 365 ℃, the heating rate is 1.5-2.2 ℃/min; after calcination, rinse and filter with distilled water for 3 times, and after drying, the negative electrode material Fe ₂ O ₃ @TiO ₂ is obtained. 2. The method for preparing an iron oxide negative electrode material for lithium-ion power batteries as claimed in claim 1, wherein in the step (1), the addition of Fe ₂ O ₃ is 3.2 g, and the addition of distilled water is 30ml, the addition amount of ethylene glycol is 30mL, the addition amount of citric acid is 10g; the addition amount of butyl titanate is 0.25-1.8ml. 3. The method for preparing an iron oxide negative electrode material for lithium-ion power batteries according to claim 2, wherein the addition amount of the butyl titanate is 0.358ml-1.702ml. 4 . The method for preparing an iron oxide negative electrode material for lithium ion power batteries according to claim 2 , wherein, in the step (2), the amount of sodium borohydride added is 0.03-0.15 g. 5 . 5 . The method for preparing an iron oxide negative electrode material for lithium ion power batteries according to claim 4 , wherein the amount of sodium borohydride added is 0.03158-0.1057 g. 6 . 6. The method for preparing an iron oxide negative electrode material for lithium-ion power batteries according to claim 1, wherein in the step (1), after drying, place in a 500°C muffle furnace for calcination for 3h, and the muffle The heating rate of the furnace was 1°C/min. 7. The method for preparing an iron oxide negative electrode material for lithium ion power batteries as claimed in claim 1, wherein in the step (2), be placed in a tubular furnace and calcined under an argon atmosphere for 1 hour, and the temperature is 350°C, the heating rate is 2°C/min.

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