Arijita Mukherjee

A lithium–oxygen battery with a long cycle life in an air-like atmosphere

Lithium–air batteries are considered to be a potential alternative to lithium-ion batteries for transportation applications, owing to their high theoretical specific energy. So far, however, such systems have been largely restricted to pure oxygen environments (lithium–oxygen batteries) and have a limited cycle life owing to side reactions involving the cathode, anode and electrolyte. In the presence of nitrogen, carbon dioxide and water vapour, these side reactions can become even more complex. Moreover, because of the need to store oxygen, the volumetric energy densities of lithium–oxygen systems may be too small for practical applications. Here we report a system comprising a lithium carbonate-based protected anode, a molybdenum disulfide cathode and an ionic liquid/dimethyl sulfoxide electrolyte that operates as a lithium–air battery in a simulated air atmosphere with a long cycle life of up to 700 cycles. We perform computational studies to provide insight into the operation of the system in this environment. This demonstration of a lithium–oxygen battery with a long cycle life in an air-like atmosphere is an important step towards the development of this field beyond lithium-ion technology, with a possibility to obtain much higher specific energy densities than for conventional lithium-ion batteries.

Vibrational Spectroscopy of Water with High Spatial Resolution

The ability to examine the vibrational spectra of liquids with nanometer spatial resolution will greatly expand the potential to study liquids and liquid interfaces. In fact, the fundamental properties of water, including complexities in its phase diagram, electrochemistry, and bonding due to nanoscale confinement are current research topics. For any liquid, direct investigation of ordered liquid structures, interfacial double layers, and adsorbed species at liquid-solid interfaces are of interest. Here, a novel way of characterizing the vibrational properties of liquid water with high spatial resolution using transmission electron microscopy is reported. By encapsulating water between two sheets of boron nitride, the ability to capture vibrational spectra to quantify the structure of the liquid, its interaction with the liquid-cell surfaces, and the ability to identify isotopes including H2 O and D2 O using electron energy-loss spectroscopy is demonstrated. The electron microscope used here, equipped with a high-energy-resolution monochromator, is able to record vibrational spectra of liquids and molecules and is sensitive to surface and bulk morphological properties both at the nano- and micrometer scales. These results represent an important milestone for liquid and isotope-labeled materials characterization with high spatial resolution, combining nanoscale imaging with vibrational spectroscopy.

Systematic Transmission Electron Microscopy Study Investigating Lithium and Magnesium Intercalation in Vanadium Oxide Polymorphs

Magnesium-ion based batteries promise a competitive alternative to conventional lithium-ion battery technology. Batteries combining Mg metal anode with a suitable intercalation-based cathode can offer much higher volumetric energy density, as well as significant cost and safety benefits over lithium ion batteries. Recent first-principles and experimental reports have established that orthorhombic α-V2O5 is a promising intercalation cathode for Mg ion batteries. However, several crucial aspects of the intercalation phenomenon, such as the specific intercalation sites for Mg within α-V2O5 or the formation of different phases upon Mg insertion into α-V2O5 remain unclear. Further systematic characterization of the Mg intercalation behaviour is therefore required.

Direct characterization of the Li intercalation mechanism into α-V2O5 nanowires using in-situ transmission electron microscopy

The Li-V2O5 system has been well studied electrochemically, but there is a lack of systematic in-situ studies involving direct investigations of the structural changes that accompany the lithiation process. The open-cell battery setup inside a transmission electron microscope is ideal for studying the reaction pathway of intercalation of Li+ into nanowire cathodes. In this work, we utilize in-situ transmission electron microscopy to study the Li-V2O5 system. More specifically, we employ electron beam diffraction and electron energy-loss spectroscopy (EELS) in an open-cell battery setup to examine the phase changes within α-V2O5 nanowire cathodes upon in-situ lithiation. Our results suggest that the pristine α-V2O5 nanowire forms a Li oxide shell which then acts as a solid state electrolyte to conduct Li+ ions, and the bulk of the V2O5 nanowire undergoes transformation to the γ−Li2V2O5 phase.

Aberration corrected STEM and High Resolution EELS study Investigating Magnesium Intercalation in Vanadium Pentoxide Cathode

Magnesium ion based batteries hold promise as a competitive alternative to conventional Lithium ion battery technology due to several key features. Theoretical volumetric capacity for magnesium metal anode is much higher compared to lithium metal. Furthermore, Mg is more readily available compared to Li, which can potentially lead to cost reduction and switching to Mg offers safety benefits over Li as well. Orthorhombic V2O5 is a well-known intercalation cathode host for Mg-ion batteries owing to its characteristic layered structure and weak vanadium oxygen bonding that facilitates ion intercalation between the layers.

Investigation of Li ion and Multivalent Battery Systems Using In situ TEM and High Resolution EELS

Energy storage research is of utmost relevance today with demands for higher energy density, faster cycling times, safer and more cost effective options. Research is underway both for exploring novel cathode materials for traditional Li ion batteries and also multivalent elements such as Mg, Ca (both divalent) or trivalent Al to replace Li ion for next generation batteries. V2O5 has been proposed as a promising cathode host for multiple reasons: its layered structure can potentially intercalate Li or other multivalent ions (e.g., Mg); a shorter Li diffusion path and high Li ion mobility has been reported for nanostructured V2O5; its theoretical energy density is higher than conventional Li ion battery electrodes; and, its low cost. [1]