Fabricating high-energy-density bimodal cathodes using radially oriented rod-shaped primary particles

Abstract

A promising approach for preparing high-energy-density Li-ion batteries (LIBs) involves the use of bimodal cathodes comprising large polycrystalline and small single-crystalline particles. Enlarging the polycrystalline secondary particles improves the tap density. However, the enlarged secondary particles generally deteriorate the rate performance when they comprise conventional polygonal primary particles, accompanied by microcracking, which further accelerates capacity fading. This study compares Ni-rich Li[Ni0.90Co0.05Mn0.05]O2 (NCM90) cathodes with different microstructures to demonstrate that challenges such as microcrack formation and poor rate capability can be effectively mitigated by a higher fraction of radially aligned rod-shaped primary particles. Furthermore, bimodal cathodes incorporating morphology-engineered polycrystalline cathodes exhibit higher mechanical strengths, reduced microcrack formation under a high calendering pressure, and superior long-term stabilities in full cell configurations than bimodal cathodes with conventional large polycrystalline cathodes. These findings highlight the importance of primary particle-level microstructural engineering and provide practical guidelines for developing next-generation high-energy-density cathodes for application in LIBs.