Abstract
Xray absorption finestructure spectroscopy was used to ascertain the individual metal oxidation states involved during the electrochemical insertion and extraction of lithium with layered LixNi0.5Mn0.5O2 electrodes in lithium cells. These results, along with electrochemical cycling data, suggest that the LixNi0.5Mn0.5O2 (0 < x ≤ 2) electrodes operate predominantly via two-electron redox couples, Ni4+/Ni2+ and Mn4+/Mn2+, between 4.5 and 2.0 V (0 < x ≤ 1) and below 1.07 V (1 < x ≤ 2) versus metallic Li, respectively. In the upper voltage region, the Ni-O bond changes by nearly 0.14 Å, while the Mn-O bond remains at nearly a fixed length. In the low-voltage region, the LiNi0.5Mn0.5O2 electrode undergoes a two-phase reaction with Li to form a dilithium compound, Li2Ni0.5Mn0.5O2; during this reaction, charge transfer occurs at the Mn metal center.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
