Search

Graphical abstract Highlights • Facile and efficient synthesis of titanate-based nanosheets and nanotubes. • Titanate nanotubes exhibits higher surface area and porosity compared to titanate nanosheets. • Incorporation of reduced graphene oxide improves the battery performance in both Li- and Na-ion configurations. • High specific capacity and fast kinetics arise from a surface structure more favorable for ion-accessibility. Abstract Electrochemical energy storage (EES) systems rely on novel materials to meet stringent performance demands in terms of both high energy and high power. Although several new materials have been identified for EES, one method that seeks to amplify material properties has been to modulate morphologies at the nanoscale. This improvement in electrochemical properties is in large part due to the enhancement in surface area and mitigation of solid-state diffusion at the nanoscale domain. By using sodium titanate (Na 2 Ti 3 O 7) as a model compound, we employ efficient synthetic routes to prepare titanate nanosheets and nanotubes, and assess their charge-storage properties in both Li- and Na-ion non-aqueous electrolytes. Moreover, nanocomposites comprising reduced graphene oxide are constructed to further enhance rate capability. We perform a fundamental electroanalytical treatment of the charge-storage properties for titanate nanosheets and nanotubes and identify the underlying rate-determining mechanisms by kinetic analysis. In both Li- and Na-ion electrolytes, the nanotube–reduced graphene oxide nanocomposite exhibits pseudocapacitive behavior, indicated by broad voltammetric features and sloping charge-discharge voltage profiles under galvanostatic mode. This corresponding charge-storage process supports high capacities of 170 and 80 mAh g−1 in a Li- and Na-ion system, respectively, based on constant current measurements at a C-rate of 5C. [ABSTRACT FROM AUTHOR]

The ion insertion properties of MoS2 continue to be of widespread interest for energy storage. While much of the current work on MoS2 has been focused on the high capacity four-electron reduction reaction, this process is prone to poor reversibility. Traditional ion intercalation reactions are highlighted and it is demonstrated that ordered mesoporous thin films of MoS2 can be utilized as a pseudocapacitive energy storage material with a specific capacity of 173 mAh g−1 for Li-ions and 118 mAh g−1 for Na-ions at 1 mV s−1. Utilizing synchrotron grazing incidence X-ray diffraction techniques, fast electrochemical kinetics are correlated with the ordered porous structure and with an iso-oriented crystal structure. When Li-ions are utilized, the material can be charged and discharged in 20 seconds while still achieving a specific capacity of 140 mAh g−1. Moreover, the nanoscale architecture of mesoporous MoS2 retains this level of lithium capacity for 10 000 cycles. A detailed electrochemical kinetic analysis indicates that energy storage for both ions in MoS2 is due to a pseudocapacitive mechanism. [ABSTRACT FROM AUTHOR]

SnO 2 nanolayer (∼10 nm) suppresses the dendritic growth of zinc and hydrogens gas evolution. [Display omitted] • Ultra-thin SnO 2 layer (∼10 nm) is deposited on Zn metal via atomic layer deposition. • The SnO 2 passivation suppresses Zn dendrite growth. • The presence of SnO 2 layer leads to hydrogen gas suppression as desired. • The SnO 2 coated Zn shows striking improvements cycling stability and rate capability than the bare Zn in aqueous zinc ion battery. Aqueous electrochemical energy storage systems that rely on earth-abundant elements are considered as cost-effective alternatives to current lithium-ion batteries which have dominated the technological landscape. For zinc-based energy storage, dendrite growth is an underlying challenge that needs to be addressed to enact high performance and long-term stability. In the present study, we employ atomic layer deposition to produce a thin tin oxide layer that allows dendrite-free cycling for aqueous zinc-ion batteries. Tin oxide is particularly interesting as it provides two distinct advantages—dendrite-free cycling and mitigation of parasitic hydrogen gas evolution. The presence of the tin oxide layer leads to hydrogen gas suppression and homogeneous zinc plating/stripping, both of which are essential to improve the performance of zinc-ion batteries. When paired in a full-cell configuration with manganese oxide, this anode delivers a high specific capacity of 273 mAh g−1 at an imposed current rate of 100 mA g−1. Through density functional theory calculations, we elucidate further that the adsorption energy of Zn for bare Zn is higher than that in the presence of a tin oxide layer. [ABSTRACT FROM AUTHOR]