Lithium-ion batteries have become the choice of power source for portable electronics and electric vehicles as they offer higher energy density than other rechargeable systems. They are also being intensively pursued for grid storage of electricity produced from renewable sources like solar and wind. Cost, safety, cycle life, energy, power, and environmental impact are the major factors in adopting them for a specific application. Among the various practically viable insertion-compound cathode chemistries available, the layered LiMO₂ (M = Mn, Ni, Co, and their solid solutions) oxides offer the highest energy density. Accordingly, there is immense interest in both academia and industry in increasing the charge-storage capacities of the layered oxide cathodes beyond the current levels. In this regard, layered oxide cathode compositions with higher nickel contents (> 50 %) are drawing much attention in recent years since Ni offers higher capacity than Co as Ni³⁺ can be oxidized fully to Ni⁴⁺ without releasing oxygen from the lattice unlike Co³⁺, which can be oxidized only to ~ 3.5+ to avoid oxygen release from the lattice. Unfortunately, compositions with high Ni contents suffer from (i) multiple phase transitions, resulting in volume change and internal stress and (ii) high surface reactivity with the organic liquid electrolyte, resulting in a growth of cell impedance and fast capacity fade during cycling. They also suffer from high surface reactivity with ambient air to form lithium hydroxide and lithium carbonate on the particle surface, which not only degrades the electrochemical performance but also severely hampers the electrode fabrication process. Innovative approaches to overcome the above challenges are needed to employ high-nickel layered oxide cathodes in practical lithium-ion cells.

This presentation will focus first on developing a fundamental understanding of the factors that control the capacity fade and air-reactivity of high-nickel layered oxide cathodes, employing samples with secondary particle sizes of ~ 10 microns and advanced bulk and surface characterization methodologies. In-depth understanding obtained with high-nickel layered oxide cathodes with Ni contents of as high as 94% and graphite anodes retrieved from full cells before and after 1,000 – 3,000 cycles based on a combination of characterization techniques, viz., X-ray photoelectron spectroscopy (XPS), time-of-flight – secondary ion mass spectroscopy (TOF-SIMS), and high-resolution transmission electron microscopy (TEM), will be presented. Utilizing the understanding gained, the presentation will then focus on the design and development of layered oxide compositions with controlled bulk and surface structures as well as new electrolytes that offer a robust interface with both the graphite anode and high-nickel layered oxide cathodes will be presented. Viability to realize lithium-ion cells with cathode capacities of as high as ~ 220 mAh/g, high power capability, and high volumetric energy density will be discussed.