Investigating Synthetic Effects on Ni-Based Oxide As a Cathode Material for Li-Ion Batteries

Lithium-ion battery (LIBs) technology has already disrupted the consumer electronic industry that has a continuous requirement on lighter weight and smaller size. Nowadays, it has been considered as the most promising power source for electric vehicles (EVs) and hybrid electric vehicles (HEVs). However, the mass adoption is still hindered by the battery performance and cost. Therefore, there is a definitive focus on increasing the energy density and lowering the cost in addition to ensure the other performance metrics such as in lifetime and safety. In the commercial Li-ion batteries, the layered transition metal oxides, such as LiCoO₂, are widely used. Despite of its high theoretical capacity (> 270 mAh/g), LiCoO₂ can only deliver about 140 - 170 mAh/g. This limited capacity as well as the high cost originated from the usage of Co has driven the research focus from LiCoO₂ to other potential alternatives.

The extensive research on the search of an alternative to LiCoO₂ has identified LiNi_xMn_yCo_zO₂ (NMCs) (0 < x, y, z < 1) as a category of promising compositions for the use of cathode materials in Li-ion batteries in terms of energy density, cost and safety. Ni content has been recognized to play a key role in an effort to push towards the high-capacity end. There have been renewed interests in this research direction. However, high Ni content causes the tendency of lithium and transition metal cation mixing and propensity to catalyze the electrolyte oxidation. Additionally, there is an evidence of preferential segregation of Ni on the surface for both NMC and Li-rich NMCs. Here we are investigating the synthetic effects on the cation distribution, and electrochemical performance of Ni-based layered oxide in a battery. The influence of synthetic routes on the bulk and surface will be systematically investigated by synchrotron XRD and soft X-ray absorption spectroscopy. These findings will hopefully shed light on the further development of Ni-based electrode materials for Li-ion batteries.