Effect of Decreasing Cobalt Content on the Electrochemical Properties and Structural Stability of Li_(1-x)Ni_(y)Co_(z)Al_(0.05)O_(2) Type Cathode Materials

TL;DR

This study uses density functional theory to show that reducing cobalt content in NCA cathodes minimally affects electrochemical performance and structural stability, supporting environmentally friendly, low-cost battery designs.

Contribution

It demonstrates that lowering cobalt in NCA cathodes from 0.15 to 0.05 has negligible impact on capacity and stability, and explores sodium doping effects.

Findings

Cobalt reduction from 0.15 to 0.05 causes negligible change in capacity.

Intercalation potential varies by only ~0.12V with cobalt reduction.

Structural stability remains unaffected by cobalt content decrease.

Abstract

In Lithium ion batteries (LIBs), proper design of cathode materials influences its intercalation behavior, overall cost, structural stability, and its impact on environment. At present, the most common type of cathode materials, NCA , has very high cobalt concentration. Since cobalt is toxic and expensive, the existing design of cathode materials is not cost-effective, and environmentally benign. However, these immensely important issues have not yet been properly addressed. Therefore, we have performed density functional theory (DFT) calculations to investigate three types of NCA cathode materials NCA_(Co=0.15), NCA_(Co=0.10), NCA_(Co=0.05). Our results show that even if the cobalt concentration is significantly decreased from NCA_(Co=0.15) to NCA_(Co=0.05), variation in intercalation potential and specific capacity is negligible. For example, in case of 50% Li concentration, voltage drop is ~0.12V while change in specific capacity is negligible. Moreover, decrease in cobalt concentration doesn't influence the structural stability. We have also explored the influence of sodium doping on the electrochemical and structural properties of these three structures. Our results provide insight into the design of cathode materials with reduced cobalt concentration, environmentally benign, low-cost cathode materials.