Abstract
One of the most challenging hurdles that the World has to face in the next decades is the sustainable use of energy. In a scenario where western societies are largely dependent of the fossil fuels for maintaining their wellness, i.e. for heating, automotive transportation and electricity production, and developing countries need to feed their growing economies, it is worth underlying both the major impact on the environment due to the indiscriminate use of such combustibles but also the geopolitical issues for the non-producing countries. Energy harvesting by renewable sources can help limiting the dependence on fossil fuel exploitation but cannot perfectly replace conventional power plant due to its intrinsic intermittency.Batteries are the devices that can draw a line under this situation, since they can stock the energy surplus when the plant is operating and then can squeeze it in the power grid when there is a lack of production. Moreover, they are also targeted to fulfil the even growing demand of energy for portable applications (mobile phones and computers, and nowadays cars and trucks). The excellent performance and the well-established technology of Lithium-ion batteries (LIBs) put them in a crucial position for supporting this new energy revolution. However their ubiquitous role has been recently questioned for two main reasons: i) of the low availability of Li, which is a rare and not-uniformly spread element that may lead to the similar problems caused by fossil fuels. And ii) the effective capacity to satisfy the highly energy-demanding applications, since Li-ion technology seems reaching is upper limit in terms of overall performance. Therefore cheaper and more powerful alternative to Li-based systems are needed.Post-Lithium-based batteries, based on other charge carriers than Li+ can be offer safer, more sustainable and performing alternative to LIBs. Mg is a promising candidate that can replace Li in electrochemical systems due to its abundance, low cost and a theoretical volume capacity twice higher than that of Li. Although the efforts devoted to the realization of a rechargeable Mg battery were made in the last 15 years, the major hurdle represented by the low compatibility between metallic Mg and conventional electrolytes still obliges the use of hazardous salt/solvent mixtures in research prototypes. Searching alternative negative electrodes to the Mg metal, i.e. compounds able to reversibly react with Mg at low potential, will pave the way for a veritable Magnesium-ion battery (MIB), allowing the use of conventional electrolytes.The present thesis is devoted to investigate the electrochemical behaviour of several p-block elements that can reversibly alloy with Mg at low potential (In, Sn, Sb, Bi). Possible synergies between these elements are also explored, realizing composite materials (Sn-Bi), or intermetallic phases (BixSb1-x and InBi) that could be employed as negative electrodes in MIBs. The chosen synthetic route for obtaining micrometric-sized particles is the mechanical milling/alloying, since it is simple, cost-effective and upscalable. Particular attention is put on the study of electrochemical mechanisms through the operando X-ray diffraction. Electrochemical performance evaluation allows selecting the best candidate for an effective test as negative electrode in MIB prototype.