LT-LiMn0.5Ni0.5O2: A Unique Co-Free Cathode for High Energy Li-Ion Cells

Abstract

Over the past decade, designing advanced, high energy density lithium-ion batteries has become necessary because of the increasing demand for electric vehicles and energy storage devices. Research efforts have focused largely on developing layered, Ni-rich cathode materials due to their high specific capacity. However, their structural and thermal instability and the relatively high cost of nickel raises a concern about their long-term viability.1 Developing next generation cathode materials, based on earth abundant elements such as manganese and iron, has therefore attracted much research interest.2 In the late 1990s, the Mn-based spinel cathode, LiMn2O4 (LMO), dominated the early development of Li-ion batteries for the electric vehicle market. The 3-D network of channels provided by the Mn2O4 spinel framework for Li+-ion diffusion channels enables a good rate performance. However, the operational capacity of Li1-xMn2O4 spinel cathodes in a lithium cell at ~4 V over the range 0<x£1 is limited by its low electrochemical capacity relative to layered cathodes. Although deep-discharging the cell at ~3 V allows the insertion of extra Li ions into the spinel framework (i.e., Li1+xMn2O4, 0£x£1), a rapid fade of capacity occurs as a result of a severe crystallographic (Jahn Teller) distortion, which prevents the use of the lower voltage reaction in commercial cells.In this presentation, a novel LT-LiMn0.5Ni0.5O2 (LT-LMNO) cathode material with unique electrochemical properties will be reported, where LT refers to its low synthesis temperature (400 °C). In striking contrast to a layered electrode with the same composition, HT-LiMn0.5Ni0.5O2 (where HT = high temperature synthesis, ~850 °C), LT-LMNO has a composite configuration with structurally-integrated lithiated spinel- and layered-like components.3, 4 It provides an electrochemical capacity almost twice that of LMO. This discovery provides a new strategy for developing next-generation. Mn-rich spinel-based cathodes.References Bianchini, M.; Roca-Ayats, M.; Hartmann, P.; Brezesinski, T.; Janek, J., There and Back Again - The Journey of LiNiO2 as a Cathode Active Material. Chem. Int. Ed. Engl. 2019, 58 (31), 10434-10458.Croy, J. R.; Gutierrez, A.; He, M.; Yonemoto, B. T.; Lee, E.; Thackeray, M. M., Development of Manganese-rich Cathodes as Alternatives to Nickel-rich Chemistries. Power Sources 2019, 434, 226706.Thackeray, M. M.; Lee, E.; Shi, B.; Croy, J. R., Review: From LiMn2O4 to Partially-Disordered Li2MnNiO4: The Evolution of Lithiated-Spinel Cathodes for Li-Ion Batteries. Electrochem. Soc. 2022, 169 (2), 020535.Shi, B.; Gim, J.; Li, L.; Wang, C.; Vu, A.; Croy, J. R.; Thackeray, M. M.; Lee, E., LT-LiMn5Ni0.5O2: A Unique Co-free Cathode for High Energy Li-ion Cells. Chem. Comm. 2021, 57 (84), 11009-11012.