Preparation And Performance Of The Solid-state Thin Film Lithium Batteries And Relative Materials

Driven by the fast development of science and technology, wearable devices,smart cards, implantable medical devices, microelectromechanical systems, and nanoelectromechanical systems have played an important and continuously increasing role in daily life. Rechargeable lithium thin film batteries(TFBs) will find a potential application as a power source in the miniaturization of electronic devices. During the last years, many potential anode materials have been prepared for thin film rechargeable lithium batteries, such as lithium metal, tin, silicon, or lithium titanium oxide. Lithium metal is not stable at high temperature. Silicon and tin exhibit insufficient cycle life caused by tremendous volume change during the intercalation and extraction of lithium ion that leads to mechanical disintegration of the electrode. These problems metioned above limit the development and practical application of lithium thin film batteries.This thesis regards lithium titanate and titanium dioxide materials which have high safety and stable structure as the main research object. The good performance lithium titanate and titanium dioxide thin film anode electrodes were prepared by radio frequency magnetron sputtering and the all solid state thin film batteries which have good charge and discharge performance were prepared with composite materials of lithium titanate and titanium dioxide, lithium manganite and lithium phosphorous oxynitride as anode, cathode and solid electrolyte,respectively. The lithium titanate thin films which have high reversible capacity and good cyclic stability during the voltage range of 0~3 V were preared using powder target than traditional ceramic target. To our knowledge, publications on all solid state thin film batteris using composite thin films of lithium titanate and titanium dioxide as anode electrodes are either rare or not available in the literature. This research altogether divides into five parts:(1) The lithium titanate thin films with amorphous structure were prepard by lithium titanate powder target. The lithium titanate thin film electrode yields good electrochemical performance in terms of high capacity of 283 mAh g-1 at a current density of 0.1 C and good cycling stability of 97% capacity retention after 100 cycles in the voltage range of 0~3 V. The lithium titanate thin films further enhance the reversible capacity and rate performanceo after nitriding. The lithium titanium oxynitride thin film had a high capacity of 290 mAh g-1 at 0.1 C, excellent rate capability of 160 mAh g-1 at 5 C and only ≈7% capacity loss after 100 cycles at 5 C charge and discharge rate.(2) The lithium titanate thin films were prepard by lithium carbonate and titanium dioxide powder mixture target. The lithium titanate thin film electrode which annealing in oxygen atmosphere exhibits an excellent rate capability of 106 mAh g-1 at an extremely high rate of 50 C and good cycling stability of 5% capacity loss after 1000 cycles at 50 C in the voltage range of 1~3 V.(3) The titanium dioxide thin films were prepard by titanium dioxide powder target. The titanium dioxide thin film which annealing in oxygen atmosphere exhibits rate capability of 92 mAh g-1 at the rate of 50 C and good cycling stability of 92 mAh g-1 and 3% capacity loss after 1000 cycles at 50 C in the voltage range of 1~3 V.(4) The composite thin films of lithium titanate and titanium dioxide were prepard by lithium titanate and titanium dioxide powder mixture target in a mass ratio of 3:2 respectively. The composite thin film which annealing in oxygen atmosphere exhibits an excellent rate capability of 110 mAh g-1 at an extremely high rate of 50 C and good cycling stability of 96% capacity retention after 1000 cycles at 50 C in the voltage range of 1~3 V. The composite thin film which annealing in argon atmosphere yields good electrochemical performance in terms of high capacity of 295 mAh g-1 at a current density of 0.1 C, good cycling stability 280 mAh g-1 and 95% capacity retention after 100 cycles in the voltage range of 0~3 V.(5) The lithium manganate thin films were prepard by lithium manganite ceramic target. The structure of the lithium manganite is typical spinel after annealing in oxygen atmosphere and showing a flat discharge platform at about 4 V. The lithium manganate thin film electrode exhibits a high capacity of 95 mAh g-1 at fisrt discharge and good cycling stability of 80 mAh g-1 after 50 cycles. The lithium phosphorous oxynitride thin films were prepard by lithium phosphate ceramic target. The structure of the lithium phosphorous oxynitride film is amorphous and the surface of film is dense. The ionic conductivity of lithium phosphorous oxynitride film is 2.5×10-7 S cm-1,and the electronic conductivity is 1.5×10-12 S cm-1. The all solid state thin film batteries were prepared with composite materials of lithium titanate and titanium dioxide, lithium manganite and lithium phosphorous oxynitride as anode, cathode and solid electrolyte, respectively. This all solid state thin film battery exhibits a high capacity of 55 mAh g-1 at fisrt discharge and good cycling stability of 35 mAh g-1 after 50 cycles in the voltage range of 0~2 V. This all solid state thin film battery will find a potential application as a safe and reliable thin film batteries in the miniaturization of electronic devices.