Modifying Li-Rich Cathodes and Investigation into Fully Earth-Abundant Cathode Materials

Abstract

The growing demand for electric vehicles and grid storage devices entails the search for materials to further enable these technologies. In this regard, the development of cost-effective, and energy-efficient lithium-ion battery cathodes is of the essence. In recent times, Ni-rich NMC oxides (LiNi x Mn y Co z O2, x+y+z = 1) have emerged as the latest and most advanced materials for use as Li-ion cathodes. However, increasing concerns over sustainability, supply chain issues, and cost-effectiveness of critical elements like Co and Ni have accelerated the search for earth-abundant, Mn and Fe-rich cathode materials.1 Lithium and manganese rich oxide materials (LMR), with general formula xLi2MnO3 • (1-x)LiMO2, can achieve higher energy densities compared to conventional NMC oxides, and thus represent attractive alternatives.2-3 Although issues like voltage fade and hysteresis are concerns with respect to practical application of LMR cathodes and have been well studied, the anomalous increase of area specific impedance (ASI) at low states of charge (SOC), has been comparatively overlooked. This presentation will discuss recent attempts to modify the low SOC ASI behavior of LMR materials by targeted substitution using Sn4+ as an example.The second part of this presentation will focus on investigations into the synthesis, structure, and electrochemical properties of layered-rock salt composites: xLi2MnO3 • (1-x)LiFeO2. Electrochemical performance of Mn-Fe rich systems is also fundamentally linked to the debated and conflicting theories of oxidation state, local structure, and migration behavior of the Fe3+/4+ red-ox couple. X-ray spectroscopic techniques have been used to address this issue. A composition-structure-property relationship is established within these systems and novel approaches are underway to further improve their electrochemical performance.References Communications Materials 2020, 1 (1), 99. Accounts of Chemical Research 2015, 48 (11), 2813-2821. Journal of The Electrochemical Society 2023, 170 (3), 030509.