Ultranarrow Bandgap Se-Deficient Bimetallic Selenides for High Performance Alkali Metal-Ion Batteries

Metal selenides have attracted significant attention as practically promising anode materials in alkali metal-ion batteries because of their high theoretical capacity. However, a drawback is that these do not provide sufficient rate performance and cycle stability for large-scale. Here, anion defect-tuned ultra-narrow bandgap bimetallic selenide nanoparticles anchored on honeycomb-like N-doped, porous carbon dominated by pyrrolic nitrogen is reported. This targeted defect chemistry and unique structure facilitate rapid diffusion of lithium-potassium ions to provide increased pseudo-capacitance that boosts electrochemical performance. It is demonstrated that in lithium- and potassium-ion batteries (LIB and KIB), the composite exhibits high specific capacity, and excellent cycle stability with a reversible capacity of 937 mA h g⁻¹ at 2 A g⁻¹ for LIB and 304 mA h g⁻¹ at 1 A g⁻¹ for KIB following 1000 cycles, together with superior rate capability of, respectively, 499 mA h g^–1 for LIB and 139 mA h g^–1 for KIB at 10 A g^–1. A synergistic effect of the greater lithium/potassium ion adsorption energy of the bimetallic selenide and N-doped carbon boosts ion diffusion kinetics of the materials is confirmed. It is concluded that, these findings will be of immediate benefit to the practical development of alkali-metal ion batteries. © 2022 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH.