In Situ Polymerized Conjugated Poly(pyrene-4,5,9,10-tetraone)/Carbon Nanotubes Composites for High-Performance Cathode of Sodium Batteries

Sodium batteries have attracted much attention in recent years because of their comprehensive electrochemical performance, high abundance, and low cost of sodium resources. However, the unsatisying energy density and poor cycling stability of current sodium batteries restrict their large-scale applications. Here an in situ polymerization method to construct pi-conjugated poly(pyrene-4,5,9,10-tetraone)/carbon nanotubes (PPTO-CNTs) composites as cathode materials for sodium batteries is used. It is found that the pi-pi interaction between PPTO and CNTs in PPTO-CNTs composites overcomes the repulsion between each PPTO unit, leading to a flat configuration of PPTO and enhancing the electronic conductivity and active sites accessibility of PPTO-CNTs composites. Thus, PPTO-CNTs electrodes display a high discharge capacity of 360.2 mAh g(-1), long cycling stability (a capacity retention of 95.1% after 1300 cycles), and high rate capability (194.5 mAh g(-1) at 10.0 A g(-1)). Moreover, a pouch-type Na//PPTO-CNTs cell with an energy density of approximate to 204.0 Wh kg(PPTO+Na)(-1) is fabricated, exhibiting a capacity retention of 91.2% after 100 cycles. In addition, the combination of experiments and theoretical calculations demonstrates the four-sodium-ion redox chemistry mechanism of each PPTO molecule unit. This work should promote the practical application of conjugated polymers in high-performance sodium batteries.