Design and synthesis of new Layered Double Hydroxides (LDHs) as new electrodes materials in lithium-ion batteries and post lithium devices

The electrification is the most probable strategy to overcome the raising problems due to the consumption of fossil fuels, but several energy storage systems are needed to complete the task. Among them rechargeable batteries play a key role for the automotive sector and their relevance is rising also for stationary applications as grid storage; in both cases the current technologies present sustainability issues related to the supply of raw materials. In this work was investigated the applicability of a new family of compounds, Layered double hydroxides (LDHs), as active anodic material both in lithium (LIBs) and sodium (SIBs) rechargeable ion batteries. Several materials were preliminary tested in LIBs following a “trial and error” approach and, among them only NiAl-NO3 and NiFe-NO3 LDHs gave enough satisfactory results to be deeper investigated. For what concern LIBs, a combined study involving classical electrochemical analysis and thermo-analytical techniques was used to explain the influence of the LDH structure on the electrochemical performances of NiFe-NO3. It was demonstrated that the presence of a bidimensional feature helps the stabilization of the material leading to high performances with a lower amount of the electrochemically active Ni. Both NiAl-NO3 and NiFe-NO3 were tested in SIBs, demonstrating their applicability in these devices. The second one was discovered to be much more stable upon the charge/discharge loops retaining a high specific capacity (~ 500 mAh/g) after 50 cycles. This discrepancy was explained, through a deep and detailed study, including in operando techniques, enlightening the stabilizing role of iron and the presence of reversible reactions involving the nitrate. The reaction mechanism for NiFe-NO3 was proposed, it was made of an initial irreversible “activation” reaction in the first sodiation followed by a mixed intercalation/conversion reversible mechanism in the following cycles. In the end, some other applications for LDHs were presented: FeMg-Cl was discovered as a potential catalyst to produce formic acid, while NiAl-citrate was investigated both for the absorption of the toxic Pb2+ from waters both as catalyst precursor. Through a pyrolysis, in fact, NiAl-citrate evolves into a metallic-Ni based material with a very high specific area (177 m2/g) that was tested as catalyst for the dry reforming of methane.