Ultra-narrow 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.

Automated summary

This study reports a dual-metal selenide nanoparticle material that alters crystal structure defects, improves the cycle stability and charge-discharge rate of alkali metal-ion batteries, and is of great significance for the practical development of these batteries.