Natural Polymer Derived Carbon Microsphere Anode for Alkali-Ion Batteries

Abstract

Rechargeable batteries are one of the most emerging energy storage techniques for the integration of renewable energy sources like solar energy and wind power. As the key members of rechargeable batteries, alkali-ion batteries have been investigated broadly due to their high safety, high energy density and environmental friendliness. Among them, lithium ion batteries (LIBs) represent one of the most mature and commercial technology in this field, however, the insufficiency of lithium resource and the growing cost become challenges to industry for large-scale energy storage applications. Recently, Na-ion batteries (NIBs) and K-ion batteries (KIBs) have been regarded as two of the most promising alternatives to LIBs, especially for large-scale energy storage, due to the abundant resource and low cost of sodium and potassium precursors. It is believed that the electrode materials are the key components in realizing high-performance batteries. For large-scale energy storage applications, electrode materials with low cost, high energy density and long cycling life are highly desired but also challenging. Here we introduce a low-cost and high-performance carbon microsphere (CM) anode derived from natural polymer for high-capacity and long-life alkali-ion batteries. The CM electrode as anode for NIBs delivers a high capacity of ~250 mAh g-1 at 30 mA g-1 and long cycling life of more than 8000 cycles without obvious decay. More appealingly, as anode for KIBs, the CM electrode demonstrates a higher capacity of ~300 mAh g-1 at 30 mA g-1, superior rate capability of over 150 mAh g-1 at an extreme current rate of 20 A g-1 and long cycling life of more than 2000 cycles. The carbon microsphere electrode demonstrated here is highly promising for large-scale energy storage applications.