Titus Masese

High energy density rechargeable magnesium battery using earth-abundant and non-toxic elements.

Rechargeable magnesium batteries are poised to be viable candidates for large-scale energy storage devices in smart grid communities and electric vehicles. However, the energy density of previously proposed rechargeable magnesium batteries is low, limited mainly by the cathode materials. Here, we present new design approaches for the cathode in order to realize a high-energy-density rechargeable magnesium battery system. Ion-exchanged MgFeSiO4 demonstrates a high reversible capacity exceeding 300 mAh·g−1 at a voltage of approximately 2.4 V vs. Mg. Further, the electronic and crystal structure of ion-exchanged MgFeSiO4 changes during the charging and discharging processes, which demonstrates the (de)insertion of magnesium in the host structure. The combination of ion-exchanged MgFeSiO4 with a magnesium bis(trifluoromethylsulfonyl)imide–triglyme electrolyte system proposed in this work provides a low-cost and practical rechargeable magnesium battery with high energy density, free from corrosion and safety problems.

Ionic Conduction in Lithium Ion Battery Composite Electrode Governs Cross-sectional Reaction Distribution

Composite electrodes containing active materials, carbon and binder are widely used in lithium-ion batteries. Since the electrode reaction occurs preferentially in regions with lower resistance, reaction distribution can be happened within composite electrodes. We investigate the relationship between the reaction distribution with depth direction and electronic/ionic conductivity in composite electrodes with changing electrode porosities. Two dimensional X-ray absorption spectroscopy shows that the reaction distribution is happened in lower porosity electrodes. Our developed 6-probe method can measure electronic/ionic conductivity in composite electrodes. The ionic conductivity is decreased for lower porosity electrodes, which governs the reaction distribution of composite electrodes and their performances.

MgFePO4F as a feasible cathode material for magnesium batteries

A stoichiometric MgFePO4F (MFPF) is synthesised by using a solid-state carbothermal method. Its monoclinic framework, possessing an entire cationic mixing of Mg2+ and Fe2+, is validated via both crystal structure analysis and simulation. Interestingly, MFPF exhibits a relatively high potential (∼2.6 V vs. Mg/Mg2+) and good cyclic stability with an encouraging capacity (∼53 mA h g−1), bringing MFPF to the fore as a promising cathode material for magnesium batteries.

Vanadium phosphate as a promising high-voltage magnesium ion (de)-intercalation cathode host

Magnesium batteries (MBs) have been considered as one of the most promising safe and low cost energy storage systems. Herein, vanadium phosphates, prepared by the electrochemical de-lithiation of Li3V2(PO4)3, are investigated as a high-voltage cathode host for Mg2+ (de)-intercalation. The reversible (de)-intercalation of Mg2+ into (from) the host structure of V2(PO4)3 are verified by the comprehensive analysis of the results from the electrochemical tests, synchrotron X-ray diffraction and absorption, and inductively coupled plasma measurements. Its exceptional high average working voltage (∼3.0 V vs. Mg/Mg2+) surpasses other reported values of cathode hosts for MBs.

A novel cationic-ordering fluoro-polyanionic cathode LiV0.5Fe0.5PO4F and its single phase Li+ insertion/extraction behaviour

A novel fluoro-polyanionic cathode LiV0.5Fe0.5PO4F is synthesized via a wet ball-milling-assisted solid state method. Cationic ordering of V3+ and Fe3+ results in a single phase behaviour over the lithium composition range of Li1±xV0.5Fe0.5PO4F (0 < x < 0.5) as revealed by X-ray diffraction analysis and electrochemical tests. This finding offers a versatile strategy of introducing single-phase behaviour in promising fluoro-polyanionic compounds exhibiting two-phase mechanisms.

Rechargeable potassium-ion batteries with honeycomb-layered tellurates as high voltage cathodes and fast potassium-ion conductors

Rechargeable potassium-ion batteries have been gaining traction as not only promising low-cost alternatives to lithium-ion technology, but also as high-voltage energy storage systems. However, their development and sustainability are plagued by the lack of suitable electrode materials capable of allowing the reversible insertion of the large potassium ions. Here, exploration of the database for potassium-based materials has led us to discover potassium ion conducting layered honeycomb frameworks. They show the capability of reversible insertion of potassium ions at high voltages (~4 V for K2Ni2TeO6) in stable ionic liquids based on potassium bis(trifluorosulfonyl) imide, and exhibit remarkable ionic conductivities e.g. ~0.01 mS cm−1 at 298 K and ~40 mS cm–1 at 573 K for K2Mg2TeO6. In addition to enlisting fast potassium ion conductors that can be utilised as solid electrolytes, these layered honeycomb frameworks deliver the highest voltages amongst layered cathodes, becoming prime candidates for the advancement of high-energy density potassium-ion batteries.The development of potassium-ion batteries requires cathode materials that can maintain the structural stability during cycling. Here the authors have developed honeycomb-layered tellurates K2M2TeO6 that afford high ionic conductivity and reversible intercalation of large K ions at high voltages.

Characterization of Neighbor Atoms

This chapter discusses the characterization technique of X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). As an example, a characterization of the charge–discharge behavior of Li2FeSiO4, which is a promising high-capacity cathode material for the next-generation lithium-ion batteries, is introduced.