Biphasic MoO <sub>2</sub> /Mo <sub>2</sub> C-Passivated Graphite Anodes for Fast-Charging Lithium-Ion Batteries
Sang Hyeok Bae, Joo Hyeong Suh, Yejin Jo, Yong Jun Cho, Min Kyung Cho, Jung Hwan Park, Min‐Sik Park, Sunho Jeong
Abstract
High Resolution Image Download MS PowerPoint Slide Fast charging of commercial lithium-ion batteries severely compromises long-term cycle durability, particularly in cells using high mass-loading thick electrodes. Such performance decay originates from interfacial kinetic limitations in the graphite anode as follows: (i) a sluggish Li + desolvation at the electrolyte–graphite interface, (ii) a hindered Li + diffusion across the solid electrolyte interphase (SEI), and (iii) a restricted Li + insertion into the graphite, which collectively lead to an undesirable Li plating. Herein, we introduce an ultrathin and uniform MoO 2 /Mo 2 C biphasic passivation layer, achieved through a sequential cationic polyelectrolyte-assisted molybdate adsorption approach. The outer MoO 2 layer does not only suppress an excessive SEI formation but also stabilizes the electrolyte interface by promoting the formation of Li 2 O and LiF-rich SEI that are both ionically conductive and chemically robust. The inner Mo 2 C layer provides a low Li + adsorption energy (−0.97 eV), a reduced surface diffusion barrier (43 meV), and a high electrical conductivity (∼10 4 S cm –1 ), consequently enabling capacitive behavior and fast intercalation kinetics at the edge plane. The biphasic layer-passivated graphite anode delivers a fast-charging capability, reaching the 80% state of charge in just 7.4 min at a current density of 6 C and retaining 78.3% of its initial capacity after 600 fast-charge cycles with a practically viable high areal capacity of 3.2 mAh cm –2 . These results represent a notable advancement over previously reported surface-engineered graphite anodes, particularly under industrially demanding conditions including high mass-loading and fast-charging.