Phd in ELECTRICAL, MATERIALS, RAW MATERIALS AND NANOTECHNOLOGY
ENGINEERING

Thesis title: Composite Anode Materials Derived from Rice Husk for Lithium- And Sodium-ion Batteries: Synthesis and Testing in Non-conventional Electrolytes

This research study is focused on the synthesis of high-capacity composite anode materials for lithium- and sodium-ion batteries using as source only rice husk (RH), a byproduct of rice harvesting. RHs have a naturally high content of Si, in the form of nanostructured particles of silica integrated into the organic matrix. The synthetized materials include C/SiO2 composites obtained by direct carbonization in Ar atmosphere at 800 and 1000°C, a disordered carbon matrix obtained by leaching with HF the RH carbonized at 800°C, C/Si composites obtained by magnesiothermic reduction (MgR) at 700°C of pre-carbonized RH using NaCl as heat scavenger varying the reduction time from 1 to 4 hours and, finally, a C/Si composite by low temperature magnesiothermic reduction assisted by a eutectic of AlC3 and NaCl. The AlCl3 actively participates in the reduction, as it was demonstrated to allow for MgR at temperature as low as 200°C in the right conditions. It was found that the effectiveness of reduction is critically dependent on the close contact of silica with reactants and the reduction chamber design. Performing the low-T reduction inside an Ar-filled 50 mL round-bottom flask, a T of at least 250°C was required to observe some SiO2 reduction. The obtained materials have been used to fabricate electrodes to be tested in half-cell configuration. Rate capabilities and cycling performance at constant current have been assessed by galvanostatic cycling with potential limitation. The electrolyte used for the half-cells were either a commercial formulation (LP30, 1M LiPF6 in EC:DMC, 1:1) or an alternative electrolyte based on a glyoxal-acetal solvent (1M LiTFSI in TEG:PC, 3:7).