High‐Voltage Performance of Ni‐Rich NCA Cathodes: Linking Operating Voltage with Cathode Degradation. Issue 22 (23rd August 2019)

• Record Type: Journal Article
• Authors: David, Lamuel; Mohanty, Debasish; Geng, Linxiao; Ruther, Rose E.; Sefat, Athena S.; Cakmak, Ercan; Veith, Gabriel M.; Meyer, Harry M.; Wang, Hsin; Wood, David L.
• Is Part Of: ChemElectroChem. Volume 6:Issue 22(2019)
• Page Start: 5571
• Page End: 5580
• Publication Date: 2019-08-23
• Subjects: Li-ion battery -- Ni-rich cathodes -- electrochemistry -- magnetic susceptibility -- in situ XRD; Electrochemistry -- Periodicals; 541.37
• DOI: 10.1002/celc.201901338
• Languages: English
• ISSNs: 2196-0216

Abstract

Abstract: High‐voltage Ni‐rich cathodes have been studied as a possible way to achieve high energy density in Li‐ion batteries. However, capacity fade due to structural changes at high voltages has limited their applications. This study identifies 4.5 V (vs. graphite) as the optimum upper cutoff voltage (UCV) for a Ni‐rich NCA cathode [LiNi0.8 Co0.15 Al0.05 O2 ]. At this UCV, NCA delivers a 12 % increase in reversible capacity (when discharged to 2.5 V) and retains 92 % of its initial capacity after 100 cycles at 1C/‐1C cycling when compared to 4.2 V as UCV. By increasing UCV to 4.7 V, the discharge capacity can be raised to >200 mAh/g. However, the rate of capacity fade is greater when compared to 4.5 V as UCV. This increased rate of capacity fade, at higher UCV, is related to irreversible lattice contractions that leads to structural rearrangement at charged states during high‐voltage cycling. Our results show a change in transition metal oxidation states and an onset of structural ordering occurs when the UCV is 4.7 V. Abstract : If I was a rich cathode : NCA lattice contraction occurs during high‐voltage cycling, which may indicate the gliding of lattice planes due to atomic structural rearrangement/modification. This phenomenon may not completely destroy the material lattice structure in the first cycle. However, the extent of lattice contraction (at higher UCV) may initiate permanent altering of the host NCA structure and cause an increase in capacity fading rate at Ni‐rich NCA cathodes.