Fe-doping on CaV₂O₆ for oxygen vacancy controlling lithium storage

Currently, alkaline earth metal vanadates as the anode materials for lithium-ion batteries (LIBs) are gradually sparking attention due to their low cost, environmental friendliness, high theoretical capacity and safety. However, their practical application is still hampered by the fast capacity degradation resulting from the prolonged cycling condition and intrinsic low electrical conductivity. Herein, single-crystal Fe-doped CaV2O6 is prepared via the low-temperature combustion synthesis route. The Fe-doping accelerates the generation of low-valence-state vanadium in CaV2O6-2%Fe, leading to the production of oxygen vacancies for maintaining electroneutrality. The versatile design of CaV2O6-2%Fe improves the electron conductivity and promotes the Li-ion diffusion rate based on the generated dual defects of interstitial atoms of Fe and oxygen vacancies accordingly. As expected, the CaV2O6-2%Fe electrode exhibits superior rate capacity of 96.6 mA h g(-1) at 5 A g(-1) and a remarkable capacity retention of 125.6 mA h g(-1) after 1000 cycles at 1 A g(-1). Additionally, the partial decomposition of CaV2O6 during the initial lithiation stage, and the formation of amorphous Li-V-O in the subsequent cycle can be used to depict the lithium storage mechanism of CaV2O6-2%Fe.