Reaserch On All-solid-state Thin Film Li-ion Batteries

As electronic devices continue to turn to be miniaturization&lightweight, a small size of the chemical power is urgently required. Particularly, with the development of micro-electrical mechanical systems (MEMS),micro-cell has attracted people's attention. Because lithium is the lightest metallic element, as well as its largest negative power, it can provide high specific energy. Meanwhile, compared with conventional batteries, all-solid-state thin film Li-ion battery can be much thiner and more flexional for its thickness can reach micrometers.What's more, it also can resolve the traditional Li-ion battery's security. Therefore, all-solid-state thin film Li-ion batteries have become the hotspot of reaserch.Using RF-MS method, using Li2Mn2O4/V2O5/Li3PO4/V, positive film/negative film/solid electrolyte film and collector film were made on substrate of glass, and experimental research on the films were done with a view to explore optimal conditions for the preparation of all-solid-state thin film Li-ion batteries. Meanwhile, thin film Li-ion batteries were prepared on substrate of organic flexible materials with plated copper in order to enhance the usefulness. The results showed that positive and negative films of Li2Mn2O4/V2O5 in sputtering atmosphere with pure Ar showed a high sputtering yield, and sputtering yields decreased with O2 mixed in, whereas the surface roughness of thin film decreased; the sputtering yields of electrolyte films of Li3PO4 sputtered in pure N2 decreased with the sputtering gas pressure increasing, but film surface roughnes increased; in different sputtering gas (pure N2, pure O2, pure Ar), sputtering yields were highest in Ar, followed by in N2, minimum in O2, the surface roughness of thin film in N2 was higher than in O2 and Ar; film-forming rate of collector V increased with sputtering power increasing, and film resistance decreased with the thickness increasing. The results also showed that thin film Li-ion batteries made on substrate of organic flexible materials with plated copper exhibited good charge/ discharge and cycle performance; as the sputtering gas pressure increasing for preparing negative film V2O5, charge/discharge and cycle characteristics turned to be stable, the discharge specific capacity increased as well, but the discharge time turned to be shorter. Finally, due to the fact that amorphous inorganic oxide-based and sulfid-based solid electrolytes were on supplementation of each other in performance, performance on multilayer structure of electrolytes so-called LiPON/Li2S—SiS2—Li3PO4/LiPON which was firstly modeled was analyzed and physical problems in these electrolytes were briefly discussed as well.The analysis showed that this multilayer structure overcomed disadvantages of each monolayer and showed higher ion conductivity,better electrochemical stability, and more superior compatibility with electrodes.