Unveiling a conversion-intercalation dual mechanism in Cr-doped TaSe₂ electrodes for high-capacity primary-secondary lithium-ion batteries

Abstract

Transition metal dichalcogenide (TMDC) flakes doped with aliovalent d-electron species provide an ideal platform for studying lithium extraction and intercalation. Drawing on design strategies for TMDC electrodes in rechargeable batteries, this work investigates Cr-doped TaSe2 (Cr0.1Ta0.9Se2) as a lithium-ion battery anode. Cr doping preserves the layered structure while introducing a dual reaction mechanism: an irreversible conversion reaction during the first discharge (contributing to high primary capacity) and a reversible intercalation process in subsequent cycles. Electrochemical tests show a high initial discharge capacity of 970 mAh g-1 at 32 mA g-1 with distinct voltage plateaus, along with stable cycling performance (222.4 mAh g⁻¹ after 500 cycles). Ex-situ XRD and XPS confirm structural evolution and Cr participation in the conversion reaction, consistent with mechanistic insights for rechargeable primary lithium batteries. This work demonstrates that targeted doping can effectively tailor TMDC electrochemistry, offering a promising route to high-capacity electrode materials with hybrid energy-storage mechanisms.