Highly Purified Carbon Derived from Deashed Anthracite for Sodium-Ion Storage with Enhanced Capacity and Rate Performance

Anthracite-derived carbon is regarded as a promising anode material for sodium-ion batteries due to the advantages of high cost effectiveness and considerable sodium storage capacity. However, originally existing impurities (such as silica and alumina) in anthracite with poor conductivity will affect the rate performance of carbon anodes; meanwhile, other metallic impurities (primarily iron) are liable to cause short circuit and jeopardize battery safety. Herein, anthracite was first subjected to a deash treatment to remove impurities followed by carbonization to prepare highly purified carbon. The deash methods and carbonization temperature were investigated in terms of the electrochemical performance. The purified carbon exhibits a high capacity of up to 252.0 mA h g–1 at 0.02 A g–1 with increasing 52.4% capacity compared with the directly carbonized sample, which can be ascribed to decrease the ash content from 9.38 to 1.00 wt %. In addition, the purified carbon anode delivers enhanced rate capacity, increasing from 63.9 to 85.8 mA h g–1 at 1.00 A g–1. The present work demonstrates that the deash method is an effective strategy to develop high-performance anodes.