(Invited) Unveiling Olivine Cathodes for High-Energy-Density Lithium-Ion Batteries: Engineering from the Atomic Level to the Electrode Scale

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The pursuit of high energy density has spurred significant interest in layered cathodes such as lithium nickel cobalt manganese oxide (NCM) or lithium nickel cobalt aluminium oxide (NCA), renowned for their excellent energy storage capabilities. However, Ni- and Co-based layered cathodes face significant thermal instability, resulting in thermal runaway in the case of short circuits, high temperature exposure, and so forth. Recently, lithium iron phosphate (LFP) has emerged as an alternative due to its enhanced structural and thermal stability, despite the absence of expensive metals such as Co and Ni. However, LFP encounters significant challenges, notably its inherently low redox potential and capacity (energy density), which undermines its competitiveness in electric device applications such as electric vehicles (EVs) and energy storage systems (ESSs). Boosting energy density can now be accomplished through the engineering of active materials and electrode configurations. It has been noticed that new strategies, such as increasing the working voltage through fine-tuning of active materials and/or using thick electrodes to augment the ratio of active materials per unit area, can make a breakthrough for elevating energy density within the existing battery volume dimension. However, transitioning to thick electrodes poses challenges related to electron and ionic conductivity, as well as the structural stability of the electrode.Herein, I will present integrating strategies for enhancing the high-energy density of olivine cathodes. This includes atomic modifications such as substitutional doping with manganese to achieve a high redox voltage, and particle/electrode engineering techniques like optimizing tap and press density. In addition, I will briefly show key technologies involving conducting agents and binders used to construct thick electrodes for olivine cathodes through eco-friendly processes. A comprehensive understanding will provide insights into how to conduct research on olivine-based cathodes and contribute to the impacts of secondary batteries in both academia and industry.