Design and characterization of doped Lithium Rich Layered Oxides for Lithium Ion Battery

Lithium-Rich Layered Oxides (LRLO) are opening new frontiers for high-capacity/high-voltage positive electrodes in Li-ion batteries to meet the challenges of green and safe transportation as well as cheap and sustainable stationary energy storage from renewable sources. LRLO exploit the extra-lithiation provided by the Li1.2TM0.8O2 stoichiometries to disclose specific capacities beyond 200-250 mAhg-1 and working potentials in the 3.4-3.8V vs Li. In my thesis, I demonstrated a novel doping strategy by the substitution of cobalt in the transition metal layer of the lattice with aluminum and lithium, resulting in new optimized layered materials, i.e. Li1.2+xMn0.54Ni0.13Co0.13-x-yAlyO2, with outstanding electrochemical performance in full Li-ion batteries, improved environmental benignity and reduced manufacturing costs compared to the state-of-the-art. Furthermore, the last step deals the application of over-lithiation to demonstrate experimentally a Co-free over-lithiated LRLO material, i.e. Li1.25Mn0.625Ni0.125O2. After that, my research focused on a novel approach to investigate the structural complexity of pristine materials, involving the use of supercells, i.e. unit cells larger than the conventional ones, and FAULTS software, to take into account the staking faults defects. A combination of ex situ techniques has been used as a tool to understand the structural evolution of Li1.28Mn0.54Ni0.13Co0.02Al0.03O2. This part of the research identified that significant changes occurred during electrochemical cycling, showed the irreversible changes in the cell parameters and the presence of a new phase. Finally, innovative non-aqueous electrolytes for Li-ion batteries with superior safety features were investigated. Three ionic liquid, Pyr1,nTFSI with n=4,5,8, have been used as addditive to improve liquid electrolytes. These electrolyte formulations have been analyzed by comparing chemical-physical properties and electrochemical stability.