Realizing the enhanced cyclability of a cactus-like NiCo2O4 nanocrystal anode fabricated by molecular layer deposition

Abstract

Lithium-ion batteries with conversion-type anode electrodes have attracted increasing interest in providing higher energy storage density than those with commercial intercalation-type electrodes. However, conversion-type materials exhibit severe structural instability and capacity fade during cycling. In this work, a molecular layer deposition (MLD)-derived conductive Al₂O₃/carbon layer was employed to stabilize the structure of the cactus-like NiCo₂O₄ nanocrystal (NC) anode. The conductive Al₂O₃/carbon network and cactus-like NiCo₂O₄ NCs are beneficial for fast Li⁺/e⁻ transport. Moreover, the Al₂O₃/carbon buffer-layer can prevent the NiCo₂O₄ NCs from agglomeration and form a steady solid electrolyte interphase (SEI), thus hampering the penetration of the electrolyte. Owing to these advantages, the assembled NiCo₂O₄@Al₂O₃/carbon half battery shows a high reversible capacity (931.2 mA h g⁻¹ at 2 A g⁻¹) and long-term stability of 290 mA h g⁻¹ at 5 A g⁻¹ over 500 cycles. Quantitative analyses further reveal the fast kinetics and the capacitance-battery dual model mechanism in the 3D core–shell structures. The design and introduction of MLD-derived hybrid coating may open a new way to conversion-type and alloy-type anode materials beyond NiCo₂O₄ to achieve high cyclability.