Combining Ab initio computation with experiments for designing new electrode materials for advanced lithium batteries: LiNi _1/3Fe _1/6Co _1/6Mn _1/3O ₂

An initial search with density functional theory to sort through potential cathode materials based on their Li intercalation potentials and electronic structures was carried on LiNi _1/3TM1 _1/3TM2 _1/3O ₂ systems, where TM1 is a 3+ transition metal (Co ³⁺, Al ³⁺, Fe ³⁺ etc.) and TM2 is a 4+ transition metal (Ti ⁴⁺, Zr ⁴⁺, Mn ⁴⁺ etc.). Fe substitution is found to be advantageous because among the compounds investigated it shows the lowest voltage at the last stage of the charge. LiNi _1/3Fe _1/6Co _1/6Mn _1/3O ₂ was synthesized by a sol-gel method and used to confirm that Fe substitution leads to a lower potential at the end of charge, Both X-ray photoelectron spectroscopy and first principles electronic structure computations indicate that Ni and Fe are simultaneously oxidized in this material. Computations further indicate that Co will only be oxidized at the very end of charge. The LiNi _1/3Fe _1/6Co _1/6Mn _1/3O ₂ compound synthesized at 750°C shows reversible capacity of ISO mAh/g with reasonably good capacity retention.