Cobalt oxide thin films for high capacity and stable Li-ion battery anode
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Here, we report reactive DC-sputter deposited Co3O4 thin films as a promising and stable Li-ion battery anode. Thin films were deposited on stainless steel by reactive sputtering of cobalt target in O2 atmosphere. X-ray diffraction and X-ray photo electron spectroscopy confirm the formation of Co3O4 crystal structure and absence of other impurities. The electron microscopy analysis shows a columnar growth morphology of the thin films while high resolution images reveal that the film is composed of ultra-small nanoparticles of average size of 5 nm. Fabricated half cells upon cycling between 3.0 and 0.01 V exhibit a stable capacity of 1125 mAh/g at a current density of 1 A/g for 100 cycles. Moreover, the electrode exhibited excellent rate capability and stability at higher rates; at current density of 10 A/g, a capacity close to 1000 mAh/g was observed. The excellent cycling stability of the cell was further confirmed by cycling at a high rate of 25 A/g (28 C) wherein the same was able to retain a capacity of 330 mAh/g even at the end of 1800 cycles. This enhanced performance could be related to the formation of 5-nm primary particles and columnar growth morphology, capable of reducing the lithium ion diffusion lengths and thus offered better kinetics even at high rates.
KeywordsAnode Co3O4 DC sputtering Li-ion battery Thin film
DS acknowledges Science and Engineering Research Board, India for awarding of Ramanujan Fellowship (Ref: SB/S2/RJN-100/2014). The PVD cluster deposition system funded by Amrita is greatfully acknowledged. APV acknowledges financial support from Department of Science and Technology, India (SR/NM/PG-01/2015).