Water intercalation strategy to fabricate low-potential and dense grapheme film anode for high energy density K-ion batteries

Abstract

Carbon materials have appealing potential as anode for Potassium ion batteries (KIBs), but achieving low-potential plateau curve and high energy density for anode materials is a primary challenge. Herein, a 3D holey reduced graphene oxide/ carbon nanotubes (L-HRGO/CNT) film was constructed via chemical etching and low- temperature drying method. The micro/mesoporous in graphene oxide (GO) sheets are created by chemical etching, which shorts ion transfer distance, and thus increases the K+ intercalation/deintercalation rate. During low-temperature drying process, the water molecules inside the GO interlayer serve as self-sacrificial spacers for extending the stacked structure and maintaining integrity, increasing capacity contributed from K+ intercalation for a low discharge voltage. And the CNTs introduced into the film via vacuum co-filtration can enhance the conductivity and mechanical strength of the film. The optimized L-HRGO/CNT film delivered a high K+ storage capacity of 307.0 mA h g−1, high-rate capability, and the capacity retention reaches 72.6% at 200 mA g−1 for 200 cycles. When assembled with the KVPO4F cathode, the reversible capacity remains 93.8 mAh g−1 after 100 cycles, and 473.0 Wh kg−1(776.9 Wh L−1) of the energy density is achieved.