High–energy-density materials that undergo conversion and/or alloying reactions hold promise for next-generation lithium (Li) ion batteries. However, these materials experience substantial volume change during electrochemical operation, which causes mechanical fracture of the material and structural disintegration of the electrode, leading to capacity loss. In this work, we use x-ray tomography during battery operation to visualize and quantify the origins and evolution of electrochemical and mechanical degradation. Tomography provides the time-resolved, three-dimensional chemical composition and morphology within individual particles and throughout the electrode. In the model material tin(II) oxide, we witness distributions in onset and rate of core-shell lithiation, crack initiation and growth along preexisting defects, and irreversible distortion of the electrode, highlighting tomography as a tool to guide the development of durable materials and strain-tolerant electrodes.

https://science.sciencemag.org/content/sci/342/6159/716.full.pdf

Visualization and quantification of electrochemical and mechanical degradation in Li ion batteries.

A critical overview of the latest developments in the aluminum battery technologies is reported. The substitution of lithium with alternative metal anodes characterized by lower cost and higher abundance is nowadays one of the most widely explored paths to reduce the cost of electrochemical storage systems and enable long-term sustainability. Aluminum based secondary batteries could be a viable alternative to the present Li-ion technology because of their high volumetric capacity (8040 mAh cm(-3) for Al vs 2046 mAh cm(-3) for Li). Additionally, the low cost aluminum makes these batteries appealing for large-scale electrical energy storage. Here, we describe the evolution of the various aluminum systems, starting from those based on aqueous electrolytes to, in more details, those based on non-aqueous electrolytes. Particular attention has been dedicated to the latest development of electrolytic media characterized by low reactivity towards other cell components. The attention is then focused on electrode materials enabling the reversible aluminum intercalation-deintercalation process. Finally, we touch on the topic of high-capacity aluminum-sulfur batteries, attempting to forecast their chances to reach the status of practical energy storage systems.

An Overview and Future Perspectives of Aluminum Batteries

The concept of exploring the superior benefits of electropositive metals as anodes in rechargeable metal-batteries has resurfaced in recent times in anticipation of the future societal need for high energy density and affordable batteries. A rechargeable battery based on aluminium chemistry is envisioned to be a low cost energy storage platform, considering that aluminium is the most abundant metal in the Earth's crust. The high volumetric capacity of aluminium, which is four and seven times larger than that of lithium and sodium respectively, unarguably has the potential to boost the energy density of aluminium-batteries on a per unit volume basis. Efforts to develop rechargeable aluminium-batteries can be traced to as early as the 1970s, however this area of research has seen a surge in activity since 2010, when the possibility of achieving an ambient temperature aluminium system was convincingly demonstrated. In recent times, rechargeable aluminium-batteries have been rechristened as aluminium-ion batteries. This review aims to comprehensively illustrate the developments regarding rechargeable non-aqueous aluminium-batteries or aluminium-ion batteries. Additionally, the challenges that impede progress in achieving a practical aluminium-ion battery are also discussed.

Aluminium-ion batteries: developments and challenges

https://iopscience.iop.org/article/10.1149/2.011211jes/pdf

Reversible Intercalation of Bis(trifluoromethanesulfonyl)imide Anions from an Ionic Liquid Electrolyte into Graphite for High Performance Dual-Ion Cells

Demonstrated here is the use of conducting polymers as active materials in the positive electrodes of rechargeable aluminum-based batteries operating at room temperature. The battery chemistry is based on chloroaluminate ionic liquid electrolytes, which allow reversible stripping and plating of aluminum metal at the negative electrode. Characterization of electrochemically synthesized polypyrrole films revealed doping of the polymers with chloroaluminate anions. Cycling of the conducting polymer electrodes occurred via the electrochemical insertion and removal of these anions. Stable galvanostatic cycling of polypyrrole and polythiophene cells was demonstrated, with electrode capacities at near-theoretical levels (30–100 mAh g–1) and Coulombic efficiencies approaching 100%. The energy density of a sealed sandwich-type cell with polythiophene at the positive electrode was estimated to be 44 Wh kg–1 relative to the total mass of active components. This energy density is competitive with state-of-the-art bat...

Chloroaluminate-Doped Conducting Polymers as Positive Electrodes in Rechargeable Aluminum Batteries

A study of the reaction pathways during electrochemical reduction of dense Nb2O5 pellets in molten CaCl2 medium

Electrochemical intercalation of aluminium chloride in graphite in the molten sodium chloroaluminate medium

Electrochemical reduction of TiO2 powders in molten calcium chloride

Electrochemical behavior of graphite in LiCl and LiCl melts containing up to 1 wt% Li2O was studied by using cyclic voltammetry and electrolysis, in the context of its probable use as anode in the electrochemical reduction of solid UO2 in the molten salt at 650◦C. The lithium deposition and chlorine evolution potentials of LiCl melt were determined by CV of tantalum (cathodic polarization) and graphite (anodic polarization) working electrodes as −2.19 V and +1.21 V vs Ni/NiO reference electrode respectively. In LiCl-Li2O melts, carbon dioxide was formed on the graphite WE from > +0.75 V onwards and its current and potential range of formation increased with increase in the Li2O content of the melt. Cathodic polarization of a UO2 disc WE in LiCl-1 wt% Li2O melt showed that the reduction of UO2 to U occurs at −2.18 V and the lithium metal deposition on it at −2.36 V. Electro-reduction experiments carried out with a dense UO2 pellet cathode and graphite anode in both LiCl and LiCl-Li2O melts proved that the surface of the pellet was reduced to U metal at ≥ −2.2 V. The reduction became increasingly difficult with increase in the Li2O content of the melt. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. [DOI: 10.1149/2.0521506jes] All rights reserved.

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K.S. Mohandas

Papers

A study of the reaction pathways during electrochemical reduction of dense Nb2O5 pellets in molten CaCl2 medium

Electrochemical intercalation of aluminium chloride in graphite in the molten sodium chloroaluminate medium

Electrochemical reduction of TiO2 powders in molten calcium chloride

A Study of Graphite as Anode in the Electro-Deoxidation of Solid UO2 in LiCl-Li2O Melt

Mechanism of Direct Electrochemical Reduction of Solid UO2 to Uranium Metal in CaCl2-48mol% NaCl Melt