Yang, C.; Lu, F.; Dong, K.; Lai, F.; Zhao, K.; Sun, F.; Dou, S.; Wang, Q.; Xu, J.; Zhang, P.; Arlt, T.; Chen, X.; Chen, Y.; Manke, I.; Guo, S.: Carbon-coated ultrathin metallic V5Se8 nanosheet for high-energy-density and robust potassium storage. Energy Storage Materials 35 (2021), p. 1-11
10.1016/j.ensm.2020.11.005
Open Access Version
Abstract:
Earth-abundant potassium is a promising alternative to lithium in energy-storage systems, but a pivotal limitation of potassium-ion batteries (KIBs) is their relatively low capacity and inferior cycle stability. Here we report the first synthesis of ultrathin metallic V 5 Se 8 nanosheets embedded in porous carbon (graphene-like V 5 Se 8 @C) as a superior anode for KIBs, which achieves a high reversible depotassiation capacity along with unprecedented rate performance and outstanding cycling stability (a reversible depotassiation capacity of 145 mAh g –1 after 800 cy- cles at 4 A g –1 with 82.9% capacity retention). The impressive performances achieved are attributed to the syner- gistic contributions of the NiAs-type superstructure, ultrathin nanosheet architecture, sufficient accessible active sites, multi-dimensional electronic/ionic transport pathways and significant pseudocapacitive behaviors. Com- bined experimental analysis and first-principles calculations reveal fast reaction kinetics, high ionic/electronic conductivity and low diffusion barriers of K-ion in graphene-like V 5 Se 8 @C hybrid. Ex-situ characterizations con- firm that V 5 Se 8 @C electrode undergo a reversible phase-evolution by the sequential intercalation and conversion reactions with synergistic K + -storage mechanisms. Furthermore, by coupling with pre-treated K 0.5 MnO 2 cathode, the full-cell is demonstrated to exhibit large energy density of 160.2 Wh kg –1 with average discharge voltage of 2.2 V and capacity retention of 86% over 200 cycles. These desirable findings demonstrate graphene-like V 5 Se 8 @C nanosheets hold great practical application in future grid-scale energy storage.