Ultra-high nickel NMC cathodes for next-generation lithium-ion batteries: Navigating the trade-offs between energy density, stability, and scalability

The expansion of LIBs for EVs and grid storage has come with a strong demand for high energy density cathodes, and this has translated to ultra-high nickel (Ni 80%) layered oxides (Li x Mn y Co z O 2 , NMC) coming to the fore. These materials have very high specific capacity (>200 mAh/g) and see a significant reduction in cobalt utilization, but high performance at commercial scale faces barriers related to trade-offs between energy density, structural stability, and manufacture ability. This review highlights the barriers that are incumbent with performing well with ultra-high nickel NMC cathodes, commonly associated with phase transitions, oxygen evolution, and transition metal dissolution and some methods for mitigating these barriers, namely core-shell structures, lattice doping, and advanced electrolyte formulations. We also report on the contributions of the SEI and CEI to stabilising high voltage solid-solid interfaces. We also highlight work with in-situ and operando characterisations which enables us to see in real time the interface and structure of ultra-high nickel NMC cathodes perform under electrochemical conditions. We examine the issues of scale up in terms of coatings technology and dry electrode processing which are also associated with the related issues of pairing these cathodes with lithium metal anodes. By examining what has been accomplished recently and what remains an issue we will provide route forward progress in overcoming performance stability barriers and ultimately progress from proof of concept (lab) scale to commercial scale. Additionally, we will put forward the position that to realize the full potential of ultra-high Ni NMC cathodes for next generation energy storage systems fully, we need to have an inter disciplinary focus.