Sb₂Te₃ hexagonal nanoplates as conversion-alloying anode materials for superior potassium-ion storage via physicochemical confinement effect of dual carbon matrix

Anode materials with conversion-alloying dual mechanism are crucial for the development of high energy density potassium-ion batteries (PIBs), while large volume expansion and poor dynamic behavior hinder its development. Herein, nanoplate-structured Sb₂Te₃ anchored on graphene and N-doped C (Sb₂Te₃@rGO@NC) is regarded as anode material for PIBs for the first time. The dual encapsulation effect of Sb₂Te₃@rGO@NC composite with strong chemical bonding of Sb—C can not only significantly restrain the large volume expansion to maintain the electrode integrity, but also efficiently enhance the electronic transfer, K-ion adsorption and diffusion ability, verified by first principles calculations and electrochemical kinetics study. As a result, the resultant Sb₂Te₃@rGO@NC electrode delivers a high initial charge specific capacity of 384.9 mAh·g⁻¹ at 50 mA·g⁻¹, great rate capability and long-term lifetime over 200 cycles at 200 mA·g⁻¹. Ex situ TEM and XPS results clarify that the electrode undergoes typical conversion-alloying dual-mechanisms with 12 mol K-ion transfer per formula employing Sb-ion as redox site (Sb₂Te₃ + 12 K⁺ + 12e^- ↔ 3K₂Te + 2K₃Sb). This work could pave the way for the fast development of Sb₂Te₃-based anode for PIBs, and help to understand the K-ion storage mechanism.