Uttam Kumar Sen

High-Rate and High-Energy-Density Lithium-Ion Battery Anode Containing 2D MoS2 Nanowall and Cellulose Binder

Electrochemically stable molybdenum disulfide (MoS₂) with a two-dimensional nanowall structure is successfully prepared by a simple two-step synthesis method followed by thermal annealing at 700 °C in a reducing atmosphere. MoS₂ nanowalls provide a better electrochemical performance and stability when cellulose (CMC) binder is used instead of the usual PVDF. The electrodes exhibit a high specific discharge capacity of 880 mA h g⁻¹ at 100 mA g⁻¹ without any capacity fading for over 50 cycles. The electrode also exhibits outstanding rate capability with a reversible capacity as high as 737 mA h g⁻¹ and 676 mA h g⁻¹ at rates of 500 mA g⁻¹ and 1000 mA g⁻¹ at 20 °C, respectively. The excellent electrochemical stability and high specific capacity of the nano structured materials are attributed to the two-dimensional nanowall morphology of MoS₂ and the use of cellulose binder. These results are the first of its kind to report a superior stability using bare MoS₂ as an active material and CMC as a binder.

Atomic Layer Deposited Molybdenum Nitride Thin Film: A Promising Anode Material for Li Ion Batteries

Molybdenum nitride (MoNx) thin films are deposited by atomic layer deposition (ALD) using molybdenum hexacarbonyl [Mo(CO)6] and ammonia [NH3] at varied temperatures. A relatively narrow ALD temperature window is observed. In situ quartz crystal microbalance (QCM) measurements reveal the self-limiting growth nature of the deposition that is further verified with ex situ spectroscopic ellipsometry and X-ray reflectivity (XRR) measurements. A saturated growth rate of 2 Å/cycle at 170 °C is obtained. The deposition chemistry is studied by the in situ Fourier transform infrared spectroscopy (FTIR) that investigates the surface bound reactions during each half cycle. As deposited films are amorphous as observed from X-ray diffraction (XRD) and transmission electron microscopy electron diffraction (TEM ED) studies, which get converted to hexagonal-MoN upon annealing at 400 °C under NH3 atmosphere. As grown thin films are found to have notable potential as a carbon and binder free anode material in a Li ion battery. Under half-cell configuration, a stable discharge capacity of 700 mAh g(-1) was achieved after 100 charge-discharge cycles, at a current density of 100 μA cm(-2).

Electrochemical activity of α-MoO3 nano-belts as lithium-ion battery cathode

Few metal oxides have seen renewed interest because of their novel reactivity towards Li, leading to a large storage capacity. However, apart from their large capacity gain, it suffers from cycling instability, large polarization loss and poor rate performance. Herein, we report on the structural, morphological and electrochemical properties of α-MoO3 nano belts prepared by a simple hydrothermal method and used as a cathode for lithium-ion battery application. During the electrode preparation, we observed that the MoO3 nano-belt composite sample cast on stainless steel (SS) substrate leads to a better electrochemical performance towards Li compared to aluminium (Al) or nickel (Ni) substrates. The reason behind the poor performance was considered here, due to surface passivation on Al substrates. This report comprises experimental results depicting (i) a sustained reversible capacity of 140 mA h g−1 for over 50 cycles at a rate of 200 mA g−1, (ii) outstanding rate capabilities with reversible capacities as high as 320 mA h g−1 at a rate of 50 mA g−1and (iii) electrochemical stability of α-MoO3 nano belts towards a stainless steel substrate. Being able to make such highly oriented α-MoO3 nano belt-based electrodes, through the hydrothermal process and providing the electrochemical results, together show another efficient way to use MoO3 electrodes as a cathode in lithium-ion batteries.

Excellent electrochemical performance of tin monosulphide (SnS) as a sodium-ion battery anode

Tin monosulphide is synthesized by a simple wet chemical synthesis approach. The as-prepared tin monosulphide has been used as anode in Na-ion battery without any in situ conductive carbon or graphene coating, and the electrode exhibits a high reversible sodium reversible capacity of ∼500 mA h g−1 at a discharge rate of 125 mA g−1. It also demonstrates excellent high rate performance (i.e. 390 and 300 mA h g−1 at 500 and 1000 mA g−1 current density respectively) and cycle stability without the addition of any expensive additive stabilizer, such as fluoroethylene carbonate (FEC), in comparison to those in current literature.

Intercalation Anode Material for Lithium Ion Battery Based on Molybdenum Dioxide

MoO2 is one of the most studied anode systems in lithium ion batteries. Previously, the reaction of MoO2 with lithium via conversion reaction has been widely studied. The present study highlights the possible application of MoO2 as an intercalation-based anode material to improve the safety of lithium ion batteries. Nanobelts of MoO2 are prepared by reduction of MoO3 nanobelts under hydrogen atmosphere. The intercalation behavior of MoO2 is specially focused upon by limiting the charge-discharge cycling to narrow potential window of 1.0 to 2.2 V vs Li/Li(+) to avoid conversion reaction. An excellent electrochemical stability over 200 cycles is achieved at a current rate of 100 mAh g(-1). A phase transformation from monoclinic to orthorhombic to monoclinic is observed during the lithiation process, which is reversible during delithiation process and is confirmed by ex-situ XRD and electrochemical impedance spectroscopy. To further demonstrate the viability of MoO2 as a commercial anode material, MoO2 is tested in a full-cell configuration against LiFePO4. The full-cell assembly is cycled for 100 cycles and stable performance is observed. The combination showed an energy density of 70 Wh kg(-1) after 100 cycles.

Intercalation based tungsten disulfide (WS2) Li-ion battery anode grown by atomic layer deposition

Thin films of tungsten sulfide (WS2) are prepared by atomic layer deposition (ALD) and its intercalation properties as an anode material in Li-ion battery are studied. The self-saturation growth of the material and the temperature window for ALD growth is confirmed by in situ quartz crystal microbalance (QCM). In situ Fourier transform infrared spectroscopy (FTIR) and residual gas analyzer (RGA) studies help to predict the two half reactions and FTIR further validates the self-limiting feature of ALD growth. The as-grown WS2 is amorphous in nature and characterized in detail by XPS and Raman spectroscopic analysis. The as-grown films are tested as a suitable intercalation based material for Li-ion battery anode. CV measurements are carried out extensively to explore the dominant intercalation property of the WS2 anode. Stable cycling performance with high coulombic efficiency (>99%) up to 100 charge–discharge cycles is observed. To enhance the performance further, multi walled carbon nanotubes (MWCNTs) scaffold layer is introduced that helps to deposit more active material for the same number of ALD cycles.

Nano Dimensionality: A Way towards Better Li-Ion Storage

Nanodimensional materials such as transition metal oxides, polyanionic based materials and metal fluorides can be used as cathode while metal nanoparticles, alloys and metal oxides are preferred as anode for next-generation lithium- ion batteries (LIBs) in order to obtain high reversible capacity, rate capability, safety, and longer cycle life. These nanomaterials can offer relatively short ionic and electronic pathways which leads to better transportation of both lithium ions and electrons to the particles core. This article emphasize on the effect of nanodimension on the electrochemical performance of cathode and anode materials. Their synthesis processes, electrochemical properties and electrode reaction mechanisms are briefly discussed and summarized. Furthermore, the article highlights recent past scientific works and new progresses in the field of LIBs. It also highlights the direction to overcome the existing issues of current lithium storage technology. In future, we may overcome all the existing issues of LIBs and can deliver excellent cathode and anode combinations to fulfill maximum practical efficiency with low cost and ultimate safety for high end applications.