Metal Oxides and Oxysalts as Anode Materials for Li Ion Batteries

Review on recent progress of nanostructured anode materials for Li-ion batteries

We developed two-step solution-phase reactions to form hybrid materials of Mn3O4 nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications. Mn3O4 nanoparticles grown selectively on RGO sheets over free particle growth in solution allowed for the electrically insulating Mn3O4 nanoparticles wired up to a current collector through the underlying conducting graphene network. The Mn3O4 nanoparticles formed on RGO show a high specific capacity up to ~900mAh/g near its theoretical capacity with good rate capability and cycling stability, owing to the intimate interactions between the graphene substrates and the Mn3O4 nanoparticles grown atop. The Mn3O4/RGO hybrid could be a promising candidate material for high-capacity, low-cost, and environmentally friendly anode for lithium ion batteries. Our growth-on-graphene approach should offer a new technique for design and synthesis of battery electrodes based on highly insulating materials.

Mn3O4-Graphene Hybrid as a High Capacity Anode Material for Lithium Ion Batteries

This is the first targeted review of the synthesis – microstructure – electrochemical performance relations of MoS2 – based anodes and cathodes for secondary lithium ion batteries (LIBs). Molybdenum disulfide is a highly promising material for LIBs that compensates for its intermediate insertion voltage (∼2 V vs. Li/Li+) with a high reversible capacity (up to 1290 mA h g−1) and an excellent rate capability (e.g. 554 mA h g−1 after 20 cycles at 50 C). Several themes emerge when surveying the scientific literature on the subject: first, we argue that there is excellent data to show that truly nanoscale structures, which often contain a nanodispersed carbon phase, consistently possess superior charge storage capacity and cycling performance. We provide several hypotheses regarding why the measured capacities in such architectures are well above the theoretical predictions of the known MoS2 intercalation and conversion reactions. Second, we highlight the growing microstructural and electrochemical evidence that the layered MoS2 structure does not survive past the initial lithiation cycle, and that subsequently the electrochemically active material is actually elemental sulfur. Third, we show that certain synthesis techniques are consistently demonstrated to be the most promising for battery applications, and describe these in detail. Fourth, we present our selection of synthesis methods that we believe to have a high potential for creating improved MoS2 LIB electrodes, but are yet to be tried.

Lithium ion battery applications of molybdenum disulfide (MoS2) nanocomposites

SnO2: A comprehensive review on structures and gas sensors

A molybdenum dioxide/multiwalled carbon nanotubes (MoO2/MWCNT) hybrid composed of spherical flowerlike nanostructures of MoO2, interconnected by MWCNTs has been prepared by a one-step hydrothermal route. The growth of MoO2 nanoparticles into spherical floral shapes with a monoclinic crystalline structure is steered by the dioctyl sulfosuccinate surfactant. The one-dimensional electron transport pathways provided by MWCNTs, which are in direct contact with MoO2 nanostructures, impart an enhanced reversible lithium storage capacity (1143 mA h g–1 at a current density of 100 mA g–1 after 200 cycles), high rate capability (408 mA h g–1 at a high C-rate of 1000 mA g–1) and good cycling stability to the MoO2/MWCNT hybrid relative to neat MoO2. Surface potential mapping of the electrodes by Kelvin probe force microscopy, revealed a lower localized work function for the MoO2/MWCNT hybrid as compared to the neat oxide. This makes the MoO2/MWCNT hybrid more easily oxidizable than neat MoO2. Such a distinctive topol...

MoO2/multiwalled carbon nanotubes (MWCNT) hybrid for use as a Li-ion battery anode.

Enhanced nanoscale conduction capability of a MoO 2/Graphene composite for high performance anodes in lithium ion batteries

SnO2 hollow spheres (HSs) were synthesized by a hydrothermal route by use of an organic additive (2-mercaptopropionic acid or MPA) and a cationic surfactant (cetyltrimethyl ammonium bromide or CTAB). The progressive transformation of SnO2 solid spheres to SnO2 HSs 140–150 nm in dimensions wherein a thin shell of densely packed SnO2 crystallites with a tetragonal crystal structure surrounds an empty core was followed by scanning- and transmission-electron microscopy. The roles of MPA as the HS structure-directing agent, CTAB as the moiety which prevents HS aggregation, and water as the solvent crucial for hollow core formation were independently determined by elaborate morphological analyses. With the goal of realizing superior electrochemical performance, hybrids of optimized SnO2 HSs embedded in graphene oxide (GO) nanosheets and enveloped by a sheath of a conducting polymer, poly(3,4-ethylenedioxythiophene) or PEDOT, were also synthesized; the continuity of the amorphous PEDOT coating on SnO2 HS/GO was ...

Poly(3,4-ethylenedioxythiophene) Sheath Over a SnO2 Hollow Spheres/Graphene Oxide Hybrid for a Durable Anode in Li-Ion Batteries

An in-situ carbon coated Li2MnSiO4/C composite was synthesized by a nanocomposite gel precursor route using starch as the carbon source. Our approach enabled a uniform coating of amorphous carbon on Li 2MnSiO4 with an orthorhombic crystalline structure, which was confirmed by electron microscopy, X-ray diffraction and Raman studies. Conducting-atomic force microscopy (C-AFM) images also revealed the presence of high current interconnected domains in the composite, indicating the ability of the carbon coating to facilitate electron movement. Galvanostatic charge-discharge studies demonstrated outstanding initial charge and discharge capacities, respectively, of 330 and 195 mAh g-1 at 0.05 C-rate for the composite, and after 30 cycles a reversible capacity of 115 mAh g -1 was retained. The electrochemical performance of the neat silicate was dismal (10.6 mAh g-1 at 0.05 C-rate), which again reiterated the role of carbon in improving the conduction and Li-ion storage capacity of the silicate. An insignificant change in charge transfer resistance, with cycling, as inferred from impedance spectroscopy illustrated that charge transfer and transport processes remain facile with cycling, thus demonstrating Li 2MnSiO4/C to be promising cathode Li-ion batteries.

In Situ Carbon Coated Li2MnSiO4/C Composites as Cathodes for Enhanced Performance Li-Ion Batteries

Tin oxide hollow spheres (SnO2 HS) with high structural integrity were synthesized by using a one pot hydrothermal approach with organic moieties as structure controlling agents. By adjusting the proportion of acetylacetone (AcAc) in the precursor formulation, SnO2 HS of 200 and 350 nm dimensions, with a uniform shell thickness of about 50 nm, were prepared. Using the optimized solution composition with a Sn precursor, heating duration dependent structural evolution of SnO2 was performed at a fixed temperature of 160 °C, which revealed a transition from solid spheres (1 h) to aggregated spheres (4 h) to porous spheres (10 h) to optimized HS (13 h) and finally to broken enlarged HS (24 h). A heating temperature dependent study carried out with a constant heating span of 13 h showed a metamorphosis from spheres with solid cores (140 °C) to ones with hollow cores (160 °C), culminating with fragmented HS, expanded in dimensions (180 °C). A growth mechanism was proposed for the optimized SnO2 HS (2.5 or 5.0 mL of AcAc, 160 °C, 13 h) and the performance of these HS as anodes for Li ions batteries was evaluated by electrochemical studies. The 200 nm SnO2 HS demonstrated an initial lithium storage capacity of 1055 mA h g−1 at a current density of 100 mA g−1, and they retained a capacity of 540 mA h g−1 after 50 charge–discharge cycles. The SnO2 HS also showed excellent rate capability as the electrode exhibited a capacity of 422 mA h g−1 even at a high current density of 2000 mA g−1. The notable capacity of SnO2 HS is a manifestation of the mono-disperse quality of the SnO2 HS coupled with the high number of electrochemically addressable sites, afforded by the large surface area of the HS and the striking cyclability is also attributed to the unique structure of HS, which is resistant to degradation upon repeated ion insertion/extraction. The SnO2 HS were also found to be luminescent, thus indicating their usefulness for not only energy storage but also for energy harvesting applications.

Tata Narasinga Rao

Papers

MoO2/multiwalled carbon nanotubes (MWCNT) hybrid for use as a Li-ion battery anode.

Enhanced nanoscale conduction capability of a MoO 2/Graphene composite for high performance anodes in lithium ion batteries

Poly(3,4-ethylenedioxythiophene) Sheath Over a SnO2 Hollow Spheres/Graphene Oxide Hybrid for a Durable Anode in Li-Ion Batteries

In Situ Carbon Coated Li2MnSiO4/C Composites as Cathodes for Enhanced Performance Li-Ion Batteries

Size-controlled SnO2 hollow spheres via a template free approach as anodes for lithium ion batteries