Open AccessInterrelationship Between the Open Circuit Potential Curves in a Class of Ni-Rich Cathode Materials
Author(s) -
Kevin Wayne Kimura,
Rebecca Wilhelm,
Münir M. Besli,
Soo Jeong Kim,
Camille Usubelli,
Jörg C. Ziegler,
Reinhardt Klein,
Jake Christensen,
Yelena Gorlin
Publication year - 2020
Publication title -
journal of the electrochemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.258
H-Index - 271
eISSN - 1945-7111
pISSN - 0013-4651
DOI - 10.1149/1945-7111/ab739c
Subject(s) - cathode , electrochemistry , nickel , lithium (medication) , stoichiometry , cobalt , materials science , analytical chemistry (journal) , inverse , open circuit voltage , battery (electricity) , chemistry , metallurgy , thermodynamics , electrode , physics , mathematics , voltage , geometry , medicine , power (physics) , chromatography , endocrinology , quantum mechanics
Ni-rich cathodes, such as nickel cobalt aluminum oxides (NCAs, Li x Ni 0.80+0.15 ε Co 0.15(1− ε ) Al 0.05 O 2 , 0 ≤ ε ≤ 1), are a class of cathode materials for lithium-ion batteries (LIBs), which are among the leading candidates for battery electric vehicle (BEV) applications. In this study we focus on an important, fundamental electrochemical property, the open-circuit potential function (OCP, U vs x), and investigate its relationship with the Ni stoichiometry. First, we demonstrate that published differential capacity curves (dQ/dU vs U) for Ni-rich NCA materials can be derived as a stoichiometric linear combination of differential capacities of the two end members, Li x Ni 0.8 Co 0.15 Al 0.05 O 2 and Li x Ni 0.95 Al 0.05 O 2 . Subsequently, the OCP curves are obtained by taking the inverse of the integrated dQ/dU vs U curves, which match literature OCP curves. Then, we apply the same method to determine the composition of an unknown cathode extracted from a commercially available LIB. Lastly, we show that the identified relationship also holds true for the Li x Ni 0.60+0.20 ε Co 0.20(1− ε ) Mn 0.20 O 2 family by demonstrating that the OCP curve of Li x Ni 0.70 Co 0.10 Mn 0.20 O 2 can be predicted from a fractional combination of Li x Ni 0.60 Co 0.20 Mn 0.20 O 2 and Li x Ni 0.80 Mn 0.20 O 2 . We anticipate that this methodology can be adapted to predict OCP curves for additional cathode families and used to validate the chemical composition of newly synthesized materials.