A Practical and Sustainable Ni/Co-Free High-Energy Electrode Material: Nanostructured LiMnO2

Ni/Co-free high-energy positive electrode materials are of great importance to ensure the sustainability of Li-ion battery production and its supply chain in addition to minimizing environmental impact. Here, nanostructured LiMnO2 with both orthorhombic/monoclinic layered domains is synthesized, and its lithium storage properties and mechanism are examined. High-energy mechanical milling is used to convert the metastable and nanosized LiMnO2 adopting the cation-disordered rocksalt structure to an optimal domain-segregated layered LiMnO2. This positive electrode produces an energy density of 820 W h kg–1, achieved by harnessing a large reversible capacity with relatively small voltage hysteresis on electrochemical cycles. Moreover, voltage decay for cycling, as observed for Li-excess Mn-based electrode materials, is effectively mitigated. Furthermore, by determining the structure–property relationships of different LiMnO2 polymorphs, LiMnO2 with similar domain structure and surface area is successfully synthesized with an alternative and simpler method, without the metastable precursor and high-energy mechanical milling. The cyclability of domain-containing LiMnO2 is also improved with the use of a highly concentrated electrolyte coupled with a lithium phosphate coating due to the suppression of Mn dissolution. These findings maximize the possibility of the development of high-energy, low-cost, and practical rechargeable batteries made from sustainable and abundant Mn sources without Ni/Co.