A vein-like nanoporous network of Nb2O5 with a higher lithium intercalation discharge cut-off voltage

Abstract

A novel morphology of a criss-cross vein-like nanoporous network of Nb 2O5 produced using a simple electrochemical anodization method is presented as a superior electrode for safe lithium-ion batteries. Scanning electron microscopy (SEM) observations demonstrate that the synthesised Nb2O5 is made of a continuous and highly packed vein-like nanoporous network with many lateral interconnections, which provides excellent channels for the fast transfer of both Li+ ions and electrons. Even without surface coating or cation doping, the porous Nb2O5 electrode could deliver durable capacity within the operating voltage window of 1.0-3.0 V vs. Li/Li+, with a reversible capacity of 201 mA h g -1 after 300 cycles at a current density of 0.4 A g-1. At the higher discharge cut-off voltage window of 1.2-3.0 V, the reversible capacity decreased to 175 mA h g-1. The first cycle Coulombic efficiency was above 94% for both operating voltage windows with a negligible capacity fading up to 300 cycles. The porous Nb2O5 electrode demonstrates several advantages as an anode including: (i) Improved cell safety due to a higher, V ≥ 1.0, discharge cut-off voltage which reduces dangerous high-temperature reactions; (ii) low level of irreversibility in the first cycle by preventing the formation of a solid electrolyte interface layer; (iii) high Coulombic efficiency due to sufficient infiltration of the electrolyte and fast diffusion of Li+ ions and (iv) high rate capability. Moreover, the synthesis method reports a novel smart design of nanostructured anode electrode materials capable of overcoming the existing limitations. Show more