A Fast-Charging and Ultra-Stable Sodium-Ion Battery Anode Enabled by N-Doped Bi/BiOCl in a Carbon Framework

Abstract

Owing to the abundant reserves and low cost, sodium-ion batteries (SIBs) have garnered unprecedented attention. However, their widespread adoption is hindered by the scarcity of alternative anodes with fast-charging capability and high stability. To overcome this challenge, a fast-charging SIB anode, N-doped Bi/BiOCl embedded in a carbon framework (Bi/BiOCl@NC) with a fast Na+ transport channel and ultra-high structural stability, is developed. During cycling in ether electrolyte, Bi/BiOCl@NC undergoes a remarkable transformation into a 3D porous skeleton, which significantly reduces the Na+ transport pathway and accommodates volume changes. By employing density functional theory calculations to simulate the storage behavior of Na+ in the structure, Bi/BiOCl@NC is theoretically characterized to have a low Na+ transport barrier (0.056 eV) and outstanding electronic conductivity. Such unique characteristics induce Bi/BiOCl@NC anode to have an ultra-high Na+ storage capacity of 410 mAh·g−1 at 20 A·g−1 and exhibit outstanding cycling stability with over 2300 cycles at 10 A·g−1. This study provides a rational scenario for the fast-charging anode design and will enlighten more advanced research to promote the exploitation of SIBs.