Mechanical densification synthesis of single-crystalline Ni-rich cathode for high-energy lithium-ion batteries

The intergranular microcracking in polycrystalline Ni-rich cathode particle is led by anisotropic volume change and stress corrosion along grain boundary, accelerating battery performance decay. Herein, we have suggested a simple but advanced solid-state method that ensures both uniform transition metal distribution and single-crystalline morphology for Ni-rich cathode synthesis without sophisticated co-precipitation. Pelletization-assisted mechanical densification (PAMD) process on solid-state precursor mixture enables the dynamic mass transfer through the increased solid-solid contact area which facilitates the grain growth during sintering process, readily forming micro-sized single-crystalline particle. Furthermore, the improved chemical reactivity by a combination of capillary effect and vacancy-assisted diffusion provides homogeneous element distribution within each primary particle. As a result, single-crystalline Ni-rich cathode with PAMD process has eliminated a potential evolution of intergranular cracking, thus achieving superior energy retention capability of 85% over 150 cycles compared to polycrystalline Ni-rich particle even after high-pressure calendering process (corresponding to electrode density of ∼3.6 g cm−3) and high cut-off voltage cycling. This work provides a concrete perspective on developing facile synthetic route of micron-sized single-crystalline Ni-rich cathode materials for high energy density lithium-ion batteries (LIBs).