One-step Solvothermal Preparation And Electrochemical Performance Of TiO₂/GNs Nanocomposites

Compared with the current commercial carbon materials, TiO₂ has the great application prospect as cathode material for lithium ion battery owing to its good safety performance, low cost, smallloss of irreversible capacity for the first time and the lack of SEI film during the charge and discharge process. However, TiO₂ has poor electrical conductivity and the TiO₂ particle is easy to agglomerate in the charging and discharging process of lithium-ion, which leads to the lithium-ion diffuses slowly in the solid active material and can’t embed and prolapse quickly. These disadvantages of TiO₂ limits its application in the power li-ion battery. Graphene（GNs） as a new type of carbon material has attracted substantial attention of researchers due to its high conductivity, large specific surface area and good environmental stability, which is ascribed to its unique two-dimensional lamellar hexagonal lattice grid structure. And the graphene-based composites are widely used in energy storage, sensors and catalysis. In recent years, some literatures about the synthesis of TiO₂/GNs composites are reported. But the synthesis and subsequent processing procedure is complex and the specific capacitance of the obtained composites is low. Therefore, the preparation of composite materials owing the simple preparation process, excellent performance and certain industrialization prospecties are very challenging and valuable. In this paper, the following three parts are included:（1） Preparation of materials: Less layer grapheme powder was prepared by Modified Hummers method. The structure and morphology of thus prepared graphene was characterized using SEM, TEM, Raman and XPS. Then anatase type TiO₂/GNs nanocomposites were synthesized using solvent hot method and the results show that anatase type TiO₂ nanoparticles were attached on the surface of graphene evenly.（2） Research of electrochemical performance: The prepared nanocomposites were mixed with Superp Li and PVDF according to certain proportion and then coated on copper foil for assembling the button batteries. The electrochemical performance of button batteries were illustrated by the constant current charge and discharge test, rate of charge and discharge test, cyclic voltammograms test and electrochemical impedance spectroscopy test. The results show that the prepared nanocomposites have the excellent electrochemical performance and outstanding high rate performance. The discharge specific capacity of nanocomposites still can reach 150mAh/g after 100 times cycle number at the rate of 10 C. At the same time, the synthetic technology and conditions of the material was optimized by testing the electrochemical performance of nanocomposites prepared using different conditions.（3） Exploration of industrialization application: The prepared nanocomposites were carried out pilot tests by the mature industrialization formulation and technology. The specific procedures included these steps such as pulping, coating, rolling, slicing, laminating, filling, sealing and then the nanocomposites were prepared into 5A soft package batteries. At last, the electrochemical performance of the soft package batteries was tested.