Three-dimensional Graphene Encapsulated Cesium Phosphotungstate Microspheres Preparation Method

Heteropoly acids, also known as polymetallic oxygen clusters, are metal-oxygen clusters formed by bridging metal atoms with oxygen atoms. The so-called Keggin-type heteropoly acid has the reversible redox property of multi-electrons. Therefore, the active capacity of the composite material used as the cathode of lithium-ion batteries reaches 260 Ah/kg, which is much higher than that of ordinary lithium-ion batteries.

It is precisely because heteropoly acid has such electron transfer form that it also shows from another aspect that poly-3-D graphene-coated cesium phosphotungstate microsphere composites as active materials of battery cathode materials have excellent charge-discharge performance. However, the intercalation and removal of lithium ions into the microcrystalline structure of heteropoly acids and the unsmooth electron transport channels of heteropoly acids lead to the poor conductivity of pure heteropoly acids, which is close to insulators.

Some scholars have proposed a method to prepare cesium phosphotungstate microspheres encapsulated in three-dimensional graphene with good electrical conductivity. The process is as follows:

1)Preparation of cesium phosphotungstate microspheres:

Cesium chloride aqueous solution was slowly added to 250 mL flask containing 100 mL 10*10-4 mol / L phosphotungstate aqueous solution with a concentration of 3*10-2 mol / L. Cesium phosphotungstate microsphere emulsion was formed by stirring at 100 ℃ for 1 h. After the reaction, cesium phosphotungstate microspheres were cooled to room temperature, filtered and separated to obtain cesium phosphotungstate microspheres.

2)Preparation of polyaniline coated cesium phosphotungstate microspheres:

The cesium phosphotungstate microspheres prepared in step 1 were taken out 0.86g and put into the polytetrafluoroethylene bottle. Then the pre-configured 10 mL 10 mg/mL graphene oxide aqueous solution was added. At room temperature, the mixed solution was stirred for an hour to react fully. Then the polytetrafluoroethylene bottle was put into the hydrothermal reactor. Finally, the hydrothermal reactor was put in. After the reaction is finished, the solid aggregates are taken out and cooled to room temperature. After freeze-drying, the prepared 3D graphene-coated cesium phosphotungstate microspheres can be obtained.

The advantages of preparing three-dimensional graphene encapsulated cesium phosphotungstate microspheres are: simple preparation method, simple operation, small size (1 micron) and uniform morphology, which are conducive to solving the problem of lithium ion intercalation and removal in microcrystalline structure. Under hydrothermal conditions, the composite materials loaded on three-dimensional sponge graphene by cesium phosphotungstate have high conductivity, good cyclic reversibility and stability in electrochemistry, and can greatly improve the capacitance of existing lithium-ion batteries.

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