S-Space College of Engineering/Engineering Practice School (공과대학/대학원) Dept. of Material Science and Engineering (재료공학부) Journal Papers (저널논문_재료공학부)
Suppression of voltage decay through manganese deactivation and nickel redox buffering in high-energy layered lithium-rich electrodes
- Ku, Kyojin; Hong, Jihyun; Kim, Hyungsub; Park, Hyeokjun; Seong, Won Mo; Jung, Sung-Kyun; Yoon, Gabin; Park, Kyu-Young; Kim, Haegyeom; Kang, Kisuk
- Issue Date
- Advanced Energy Materials, Vol.8 No.21, p. 1800606
- layered lithium-rich nickel manganese oxides; Mn deactivation; phase transformation; redox buffers; voltage decay
- Cobalt-free layered lithium-rich nickel manganese oxides, Li[LixNiyMn1-x-y]O-2 (LLNMO), are promising positive electrode materials for lithium rechargeable batteries because of their high energy density and low materials cost. However, substantial voltage decay is inevitable upon electrochemical cycling, which makes this class of materials less practical. It has been proposed that undesirable voltage decay is linked to irreversible structural rearrangement involving irreversible oxygen loss and cation migration. Herein, the authors demonstrate that the voltage decay of the electrode is correlated to Mn4+/Mn3+ redox activation and subsequent cation disordering, which can be remarkably suppressed via simple compositional tuning to induce the formation of Ni3+ in the pristine material. By implementing our new strategy, the Mn4+/Mn3+ reduction is subdued by an alternative redox reaction involving the use of pristine Ni3+ as a redox buffer, which has been designed to be widened from Ni3+/Ni4+ to Ni2+/Ni4+, without compensation for the capacity in principle. Negligible change in the voltage profile of modified LLNMO is observed upon extended cycling, and manganese migration into the lithium layer is significantly suppressed. Based on these findings, we propose a general strategy to suppress the voltage decay of Mn-containing lithium-rich oxides to achieve long-lasting high energy density from this class of materials.
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