Oxygen vacancy-enriched V-doped β-MnO2 as cathode for lithium primary batteries

Abstract

As a promising cathode material for Li/MnO₂ primary batteries, β‑MnO₂ suffers from sluggish ion diffusion kinetics and limited high‑rate capability. Vanadium doping is herein proposed to tune its crystal structure and electrochemical performance. Hollow porous V-doped β‑MnO₂ microspheres rich in oxygen vacancies were synthesized via a hydrothermal route combined with two-step calcination. Structural characterizations reveal that 2% V doping maintains the intrinsic crystal phase of β-MnO₂ while simultaneously triggering lattice expansion, enlarging the specific surface area and generating abundant oxygen vacancies. Four-probe electrical measurements and GITT confirm the enhanced electronic conductivity and Li⁺ ionic transport in V-modified β-MnO₂, respectively. Electrochemical measurements demonstrate that the 2%V-MnO₂ cathode exhibits discharge capacities of 249.1 mAh g^− 1 at 0.1 C and 223.3 mAh g^− 1 at 1 C, corresponding to a capacity retention of 89.6%. Such electrochemical performance surpasses that of pristine MnO₂ and 4%V-MnO₂ samples. High-temperature aging storage experiments verify that moderate V doping significantly suppresses self-discharge and improves the long-term shelf stability of the battery. DFT calculations elucidate that V doping lowers oxygen vacancy formation energy and narrows band gap of β-MnO₂. This study demonstrates that moderate V doping combined with the hollow porous structure can synergistically accelerate electron transport and ion diffusion kinetics of β-MnO₂, providing a feasible pathway for developing high-power cathode materials for Li/MnO₂ primary batteries.