Nanostructured LiNi_0.80Co_0.15Al_0.05O₂ (NCA) for fast-charging, high-capacity battery cathodes

Nanostructuring, which shortens lithium-ion diffusion lengths, can help facilitate pseudocapacitive behavior in some battery materials. Here, nanostructured LiNi_0.80Co_0.15Al_0.05O₂ (NCA), with porosity and decreased crystallite size compared to commercial bulk NCA, was synthesized using a colloidal polymer template. Small particles (∼150 nm) were obtained using rapid thermal annealing (RTA), while medium particles (∼300 nm) were obtained with conventional heating. X-ray photoelectron spectroscopy (XPS) was used to quantify surface Li₂CO₃ and NiO-like contaminants, which hinder lithium-ion diffusion, especially at fast rates. Electrochemical kinetics studies were used to quantify the benefits associated with nanostructuring. While all nanostructured samples displayed faster charge/discharge kinetics compared to the bulk materials, NCA with medium particle sizes showed the highest specific capacity at the fast rates (150 mAh g^-1 at 16C). To explore full-cell behavior, nanostructured NCA was paired with a pseudocapacitive anode, achieving 95 W h kg^-1 energy density at a current density of 1260 W kg^-1 and stable cycling for 2000 cycles at 10C.