Woven microsphere architected by carbon nanotubes as high-performance potassium ion batteries anodes

Abstract

Owing to the abundance of potassium resources and compared performance to Lithium-ion batteries (LIBs), Potassium ion batteries (KIBs) are becoming an important supplement to the energy market dominated by LIBs now. Graphitic carbon is a mainstream anode material for LIBs, and also has great potential as anode of KIBs. But due to the limited layer spacing of graphitic carbon, the intercalation of large K+ results in poor rate and low temperature performance and limited life of battery. Here, microspheres knitted by robust carbon nanotubes (CNTs) are constructed through one step injected pyrosis using thiophene as both carbon and co-catalyst source, ferrocene as both catalyst precursor and part carbon source and followed by graphitization, finally giving graphitic carbon with both toughness and rapid ionic conductivity. When used as the anode of KIBs, it presents a stable and slight increased capacity of 155.5 mAh g−1 after 1000 cycles at 1C due to stability of unique structure. It is proven that local amorphization of carbon in the pore increases more K+ storage active sites, resulting an increased capacity with cycle. Moreover, the anode can achieve high power density with depotassiated capacity of 164.3 mAh g−1 as current density high as 70C (less than 1 min) and outstanding low temperature performance with 167.8 mAh g−1 at −40℃, proving its super dynamic and potential in low temperature scenarios. All in all, the unique structurally engineered graphitic carbon provides an insightful idea to promote the further application of graphite anode for KIBs.