Mechanistic insights into suppressing microcracks by regulating grain size of precursor for high-performance Ni-rich cathodes

Abstract

Layered Ni-rich transition metal oxides (LiNixCoyMnzO2, x + y + z = 1, NCM) are regarded as promising cathodes for high-energy Li-ion batteries, due to merits of large capacity and low cost. However, the formed microcracks during cycling can lead to severe structural degradation, rapidly deteriorating properties of NCM cathode. To solve this problem, an enhanced mechanical strength strategy triggered by regulating the grain size of precursor has been successfully proposed, which is aimed at improving the structural stability of NCM cathode. It is found that NCM cathode featured with small grain size (NCM-S) exhibits a strong mechanical property for hindering structural deterioration. Detailedly, the strong external compression rupture strength triggered by grain size effect and decreased internal stress originating from mitigated H2-H3 phase transition are both beneficial for synergistically suppressing the generation of microcracks. Benefiting from the unique architecture, the NCM-S cathode delivers a remarkable initial discharge capacity of 192.6 mAh g−1 at 0.1C and excellent capacity retention of 82.8 % after 300 cycles at 1C. This work powerfully provides a mechanistic perspective based on the regulating precursor grain size for impeding the structure collapse, which is beneficial for purposefully engineering the high-performance Ni-rich cathodes in electric vehicles.