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Singapore, Singapore

Reddy M.V.,Ionics | Reddy M.V.,Graphene Research Center | Reddy M.V.,National University of Singapore | Prithvi G.,Ionics | And 3 more authors.
ACS Applied Materials and Interfaces | Year: 2014

The compounds, CoN, CoO, and Co3O4 were prepared in the form of nano-rod/particles and we investigated the Li-cycling properties, and their use as an anode material. The urea combustion method, nitridation, and carbothermal reduction methods were adopted to prepare Co3O 4, CoN, and CoO, respectively. X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and the Brunauer-Emmett-Teller (BET) surface and density methods were used to characterise the materials. Cyclic voltammetry (CV) was performed and galvanostatic cycling tests were also conducted up to 60-70 cycles. The observed reversible capacity of all compounds is of the increasing order CoO, Co 3O4, CoN and all compounds showed negligible capacity fading. CoO allows for Li2O and Co metal to form during the discharge cycle, allowing for a high theoretical capacity of 715 mA h g-1. Co3O4 allows for 4 Li2O and 3Co to form, and has a theoretical capacity of 890 mAhg-1. CoN is the best anode material of the three because the nitrogen allows for Li3N and Co to form, resulting in an even higher theoretical capacity of 1100 mAhg-1 due to the Li3N and Co metal formation. Irrespective of morphology the charge profiles of all three compounds showed a major plateaux ∼2.0 V vs. Li and potential values are almost unchanged irrespective of crystal structure. Electrochemical impedance spectroscopy (EIS) was performed to understand variation resistance and capacitance values. © 2013 American Chemical Society. Source

Reddy M.V.,National University of Singapore | Rajesh M.,National University of Singapore | Rajesh M.,St Andrews Junior College | Adams S.,National University of Singapore | Chowdari B.V.R.,National University of Singapore
ACS Sustainable Chemistry and Engineering | Year: 2016

We have prepared CuCo2O4 using 0.5 M NaNO3 and 0.5 M LiNO3 molten salts at different temperatures (410 and 610 °C) in the air. This was later used as an anode material for LIBs. The morphology, structure, and electrochemical properties of the products were observed using various techniques such as scanning electron microscopy, X-ray diffraction (XRD), Brunauer-Emmett-Teller surface and density method, cyclic voltammetry, and galvanostatic cycling tests. The XRD patterns showed a minor CuO phase in addition to the major CuCo2O4 phase in most of the reactant and salt combination. CuCo2O4 prepared using copper sulfate and cobalt sulfate at 610 °C and copper sulfate and cobalt acetate at 410 °C showed the best performance with capacities of 848 mAh g-1 and 882 mAh g-1 and capacity retentions of 93% and 94%, respectively. © 2016 American Chemical Society. Source

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