Design and synthesis of PbBiVO5 electrode by polymorph engineering for rechargeable battery

Highlights: • A newly-synthesized Bi-based oxide demonstrates particularly promising candidates as electrode material. • Both designed polymorphs PbBiVO₅ with similar structure units displays distinctly different electrode performance. • Advantageous arrangements of Bi atoms generate advantageous electronic structures and charge transfer. • Rational structure arrangement provides a feasible strategy for advanced energy storage devices. Polymorphism existing in more than one form or crystal structure exerts a profound influence on electrochemical properties. Bi-based oxides demonstrate variable coordination geometries and particularly promising candidates as electrode materials. Both designed polymorphs α- and γ- PbBiVO₅ consist of BiO₆ polyhedra, PbO₆ polyhedra and VO₄ tetrahedra. In α-PbBiVO₅, the BiO₆ and PbO₆ polyhedra form zigzag [Bi₂Pb₂O₁₂]_∞ chains bridged by VO₄ tetrahedra, while in γ-PbBiVO₅, the BiO₆ and PbO₆ polyhedra separately form [BiO₄] _∞ and [PbO₄]_∞ chains bridged by VO₄ tetrahedra. Interestingly, γ-PbBiVO₅ has a specific capacitance of 85 mAh g⁻¹ at a current density of 0.5Ag⁻¹, better than that of α-PbBiVO₅ by cal. 21%. Theoretical calculations reveal that γ-PbBiVO₅ at the exposed surface (011) nearly becomes conductor with bandgap as narrow as 0.02eV, elucidating the enhanced electrode performance. Bader charge analysis illustrates that the [BiO₄]_∞ chains facilitate more charge transfer. The electrode from the optimized composite of γ-PbBiVO₅@5wt% hydrogenated graphene flakes (HG) delivers a high specific capacity of 96mAhg⁻¹ at the current density of 0.5Ag⁻¹ and capacity retention of about 87.6% after 1000 cycles. The assembled batteries power a 3V white LED. Rational structure arrangement provides a feasible strategy for advanced energy storage devices.