(Invited) Cobalt Free Li-Ion Battery Cathode Materials for Next Generation Electric Vehicles

Abstract

The battery manufacturing industry has a cobalt problem! Over the recent years, rapid fluctuations in cobalt prices have created a drastic supply chain constraint that threatens to derail the burgeoning projections for electric vehicles over the next few decades. To reduce the cost of modern batteries to ~80$/kWh (to sustain the growing electric vehicle demands), it has become paramount that the amount of cobalt, the most expensive present-day battery cathode raw material, should be reduced to less than 50 mg at the cell level. Moreover, it is also important that any alternative cathode material developed, should facilitate a seamless integration into existing global battery manufacturing infrastructures to avoid a complete overhaul. The search for viable alternatives that address these challenges simultaneously is a continuing quest in today's battery research and development sectors. In this context, our team through a paradigm shifting approach has developed a new class of layered lithium ion battery cathode material with '0' cobalt in its composition. This new class of battery cathodes, termed the NFA class, has the general formula, LiNixFeyAlzO2 (where, x + y + z = 1)[1,2]. These layered cobalt-free cathodes are analogous in crystal structure and material properties to mainstream cobalt containing cathodes such as NCMs and NCAs while delivering comparable and in some cases better electrochemical performance. Here, I will present our efforts in the systematic development of these novel cathodes starting from compositional landscape investigations and advanced characterizations employing NFA material synthesized using the lab-scale sol-gel process. Through our approach, in-situ high temperature X-Ray and Neutron diffraction techniques were used to investigate the calcination and phase formation behavior while operando investigations using X-Ray diffraction and Mössbauer spectroscopy were employed to obtain a mechanistic understanding of the charge/discharge process of this new cobalt-free cathode material. Following these, the most promising compositional variants were upscaled using the co-precipitation process in continuous stirred tank reactors for obtaining kg levels of cathode material. Systematic optimization of reaction process variables ensured good particle morphologies, homogeneities and composition control. Electrochemical performance assessments performed in both half-cell and full-cell configurations tested in different voltage windows with upper cut-off voltages ranging from 4.1V to 4.5V demonstrated that the optimized NFA compositional variants deliver high capacities >200 mAh/g at 0.1C with good capacity retention >80% when cycled at C/3. Full pouch-cells (>1.5Ah) were then assembled using NFA electrodes fabricated using the slot-die coating technique with the upscaled cathode material demonstrating reasonable capacity retentions[3]. While the work presented here is still in an early stage of research, the immense potential that these NFA class of cathodes could have as viable candidates towards development of next generation cost effective lithium ion batteries is highlighted here. Overall, our research efforts in the development of this new class of cobalt-free cathodes aims to mitigate the battery industry's cobalt problem paving a promising pathway towards the wide adoption of electric vehicles in the coming decades.