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Exploring novel electrode materials is critical for the development of a next-generation rechargeable magnesium battery with high volumetric : capacity. Here, we showed that a distinct amorphous molybdenum sulfide, :being a coordination polymer of disulfide-bridged (Mo3S11) clusters, has great,potential as a rechargeable magnesium battery cathode.. This material provided good reversible capacity, attributed to its unique structure with high flexibility and capability of deformation upon Mg insertion. Free terminal disulfide moiety May: act as the:active site for reversible insertion and, extraction of magnesium. Refereed/Peer-reviewed

Olivine-type LiMPO4 (M - Fe, Mn, Co and Ni) cathode materials hold promise for next-generation of lithium-ion batteries and future applications as hybrid electric vehicles or electric vehicles. In lithium intercalation olivine compounds, the lithium diffusion along a channel is highly anisotropic which is mainly confined to the channel along the [010] direction. Thus, nanosheets or nanoplates with shortened Li ion diffusion distance along the [010] direction are enabled to accelerate the lithium intercalation rate and improve power density of the batteries. Herein, we report the production of high-quality thin LiMPO4 nanoplates with exposed {010} facets by a rapid supercritical fluid processing. The unique structure of the olivine nanocrystals with a shortened Li ion diffusion pathway allows fast extraction/insertion of Li ions in the structures. Thus, the LiMPO4 nanoplates provide high capacity and high rate capacity and excellent cyclability. Refereed/Peer-reviewed

Li 2 CoPO 4 F cathode materials have been synthesized by a two-step method combining a sol-gel route and solid state reaction. X-ray diffraction (XRD) analysis confirmed that the Li 2 CoPO 4 F was well-crystallized in orthorhombic crystal structure with Pnma space group. From the high resolution transmission electron microscopy (HRTEM) image; the lattice fringes of {001} and {100} are well-resolved. HRTEM image and selected area electron diffraction (SAED) pattern reveal the highly crystalline nature of Li 2 CoPO 4 F having an ordered orthorhombic crystal structure. The Co atoms chains of Li 2 CoPO 4 F have been observed using high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The Raman and Fourier transform infrared spectroscopy (FTIR) spectra indicate the symmetry and stability of the Li 2 CoPO 4 F structure. The Li 2 CoPO 4 F cathode materials delivered an initial discharge capacity of 91 mAhg −1 at C/10 rate with good cyclic performance. The discharge profile of Li 2 CoPO 4 F shows a plateau at 5.0 V; revealing its importance as potentially high-voltage cathode.

The point defects in crystal lattices including antisite cation exchange, dopants, and atomic vacancies have been the topic of extraordinary research interest in solid state physics and chemistry. The ordered olivine structure was maintained after delithiation as indicated in high-resolution TEM images and selected-area electron diffraction (SAED) patterns. The increased degree of defect suggests that the cobalt metal ions have diffused and occupied vacancies created by Li extraction during the delithiation process. The extraction of Li ions from the lattice promotes the relocation of Co ion from M2 sites to the vacancy M1 sites. The vacancies created by Co ions migration appear to be locally segregated in the channel. The relocation resulted in the large capacity loss (low coulomb efficiency) in the initial discharge process. Refereed/Peer-reviewed

LiCoPO4 nanocrystals are synthesized via a supercritical fluid process at 380 degrees C for 1 h and we visualize Li/Co antisite defects along two crystallographic directions using annular dark and bright field scanning transmission electron microscopy (STEM). The antisite defects are observed with bright/dark contrast produced by Co atoms in Li columns in both HAADF (high angle annular dark field) and ABF (annular bright field) images viewed along [010] directions. Interestingly, few antisite defects are observed along [101] directions with weak contrast and P atoms are observed near to Co atoms. Refereed/Peer-reviewed

Lithium manganese silicate positive electrode materials have received great attention because of the two lithium ion capacities and can be realized in ultrafine nanoparticles due to their low volumetric changes upon lithium insertion and extraction. A supercritical fluid process has been adopted to synthesize monodisperse Li2MnSiO4 ultrafine particles and hierarchical nanostructures with a mean particle diameter of 4-5 nm and successfully shown to attain a high electrochemical performance. A reversible capacity (190-220 mA h g(-1)) of more than one lithium ion was obtained for the ultrafine monodisperse nanoparticles and hierarchical nanostructures with good cyclability. The enhanced cyclability was found to be due to the monodisperse nanoparticles, which provide a short length for Li-ion diffusion, and possess low volumetric changes. In addition, the varyingly sized Li2MnSiO4 particles were also synthesized via a supercritical fluid process. This process is simple, rapid, energy saving and broadly applicable to other functional materials. Refereed/Peer-reviewed

Positive electrodes such as LiFePO4 and LiMnPO4 nanomaterials with olivine structures are considered as most efficient cathode materials for application in lithium ion batteries. Recently, several methods have been proposed for the preparation of lithium metal phosphates as cathodes for lithium ion batteries and their electrochemical performances have been investigated. Over the last 20 years, several synthetic methods have been proposed for lithium metal phosphate nanomaterials. In this review, hydrothermal and solvothermal syntheses of LiFePO4 and LiMnPO4 nanomaterials at low and high temperatures are discussed, including microwave-hydrothermal and microwave-solvothermal methods. The effect of particle size and particle morphology on the electrochemical properties of LiFePO4 and LiMnPO4 cathode materials are also discussed. In addition, the recently emerged supercritical solvothermal and supercritical hydrothermal syntheses of LiFePO4 and LiMnPO4 nanomaterials and their electrochemical property also been addressed. Refereed/Peer-reviewed

Structural studies of high voltage cathode materials are necessary to understand their chemistry to improve the electrochemical performance for applications in lithium ion batteries. LiNiPO4 nanorods and nanoplates are synthesized via a one pot synthesis using supercritical fluid process at 450 oC for 10 min. The X-ray diffraction (XRD) analysis confirmed that LiNiPO4 phase is well crystallized, phase purity supported by energy dispersive spectroscopy (EDS) and elemental mapping by scanning electron transmission electron microscopy (STEM). For the first time, we have carried out direct visualization of atom-by-atom structural observation of LiNiPO4 nanomaterials using high-angle annular dark-field (HAADF) and annular bright-field (ABF) scanning transmission electron microscopy (STEM) analysis. The Rietveld refinement analysis was performed to find out the percentage of antisite defects presents in LiNiPO4 nanoplates and about 11% of antisite defects were found. Here, we provide the direct evidence for the presence of Ni atoms in Li sites and Li in Ni sites as an antisite defects are provided for understanding of electrochemical behavior of high voltage Li ion battery cathode materials.

Atomic-resolution imaging of the crystal defects of cathode materials is crucial to understand their formation and the correlation between the structure, electrical properties, and electrode performance in rechargeable batteries. The polytype, a stable form of varied crystal structure with uniform chemical composition, holds promise to engineer electronic band structure in nanoscale homojunctions.1-3 Analyzing the exact sites of atoms and the chemistry of the boundary in polytypes would advance our understanding of their formation and properties. Herein, the polytype and stacking faults in the lithium cobalt silicates are observed directly by aberration-corrected scanning transmission electron microscopy. The atomic-scale imaging allows clarification that the polytype is formed by stacking of two different close-packed crystal planes in three-dimensional space. The formation of the polytype was induced by Li-Co cation exchange, the transformation of one phase to the other, and their stacking. This finding provides insight into intrinsic structural defects in an important Li2CoSiO4 Li-ion battery cathode. Refereed/Peer-reviewed

LiCoPO4 cathode materials have been synthesized by a sol-gel route. X-ray diffraction analysis confirmed that LiCoPO4 was well-crystallized in an orthorhombic structure in the Pmna space group. From the high-resolution transmission electron microscopy (HR-TEM) image, the lattice fringes of {001} and {100} are well-resolved. The HR-TEM image and selected area electron diffraction pattern reveal the highly crystalline nature of LiCoPO4 having an ordered olivine structure. The atom-by-atom structure of LiCoPO4 olivine has been observed, for the first time, using high-angle annular dark-field (HAADF) and annual bright-field scanning transmission electron microscopy. We observed the bright contrast in Li columns in the HAADF images and strong contrast in the ABF images, directly indicating the antisite exchange defects in which Co atoms partly occupy the Li sites. The LiCoPO4 cathode materials delivered an initial discharge capacity of 117 mAh/g at a C/10 rate with moderate cyclic performance. The discharge profile of LiCoPO4 shows a plateau at 4.75 V, revealing its importance as a potentially high-voltage cathode. The direct visualization of atom-by-atom structure in this work represents important information for the understanding of the structure of the active cathode materials for Li-ion batteries. Refereed/Peer-reviewed

Novel ultrathin Li2MnSiO4 nanosheets have been prepared in a rapid one pot supercritical fluid synthesis method. Nanosheets structured cathode material exhibits a discharge capacity of similar to 340 mAh/g at 45 +/- 5 degrees C. This result shows two lithium extraction/insertion performances with good cycle ability without any structural instability up to 20 cycles. The two-dimensional nanosheets structure enables us to overcome structural instability problem in the lithium metal silicate based cathode materials and allows successful insertion/extraction of two complete lithium ions. Refereed/Peer-reviewed

The best of both worlds: Graphene/ionic liquid (G-IL) layered films were obtained by direct reduction of graphene oxide in the presence of ionic liquids, followed by reassembly through electrostatic layer-by-layer (LbL) adsorption (see picture). The layer spacing of the graphene sheets is regularly expanded upon insertion of ionic liquid molecules (green discs). Selective sensing of aromatic compounds (red spheres) by using the G-IL LbL films was also achieved. Refereed/Peer-reviewed

Monodispersed Li2MnSiO4 nanoparticles are synthesized via a supercritical solvothermal method at 300 degrees C for 5 min reaction time. The as-synthesized nanoparticles are free from impurities and have 15-20 nm diameter. After coating with conductive polymer, a discharge capacity of 313 mA h g(-1) is obtained for the first time because of nearly 2Li(+) reaction. Refereed/Peer-reviewed