Composite NiO-NiSe Thin Film Fabricated by Pulse Laser Deposition as a New Anode of Lithium Ion Batteries

In 2000, Tarascon et al. revealed the reversible conversion reaction based on the size effect of nanoparticles in metal oxide system, whose theoretical capacity is up to 1000mAh·g^-1[1]. However, except large capacity, metal oxide as anode material has its own drawbacks. For example, the electronic conductivity of metal oxides is usually poor, and some of them will form alloy with lithium during the reaction process which cause huge volume change. In order to overcome these obstacles, lots of methods have been presented. Mainly includes the following ways: 1) Fabricating thin film materials, 2) Synthesizing nanostructured materials, 3) Doping or preparing composite materials. Further works showed the doping is effective and convenient in thin film fabrication, and the composite thin films usually obtained better performance than the single system.

NiO-NiSe nanocomposite films were fabricated by plused laser deposition. Charge/discharge measurements, cyclic voltammograms and AC impedance tests were used to investigate cyclic performance and electrochemical properties of the materials. X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) were employed to detect the structure, morphology and composition of these nanocomposite films in certain electrochemical states. In addition, the electrochemical reaction mechanism of the films versus Li were discussed.

The results indicated that: Compared with the single system NiO or NiSe, the transfer resistance of lithium ion in NiO-NiSe nanocomposite thin film is smaller. NiO-NiSe electrode also exhibited a little higher discharge-charge capacity and better cycle performance. After 50 cycles, a reversible  capacity of 495mAh.g^-1 can still be obtained. NiO-NiSe nanocomposite film also has good rate capability and is more suitable for lithium-ion battery anode material. The electrochemical reaction mechanism investigation showed that NiO and NiSe in the electrode reacted with lithium separately and could be reversibly reproduced.