Spray drying derived wrinkled pea-shaped carbon-matrixed KVP2O7 as a cathode material for potassium-ion batteries

Searching for advanced cathode materials is indispensable for the eventual practical applications of potassium-ion batteries (KIBs). Herein, we design and synthesize a carbon-matrixed potassium vanadium pyrophosphate powder (KVP2O7@C) with a wrinkled pea-shaped particle morphology via a spray drying process. As a cathode material for KIBs, this KVP2O7@C exhibits a reversible capacity of 60 mA h g(-1) with two discharge plateaus at 4.1 V and 4.5 V (vs. K+/K), leading to a high energy density of 250 W h kg(-1) at 0.2 C in half cells. The potassium storage mechanism of KVP2O7 is revealed by ex-situ X-ray diffraction technology as an intercalation/de-intercalation reaction during electrochemical cycling, i.e. KVP2O7 (P2(1)/c + P1) <-> KxVP2O7 (x approximate to 0.4, P1). A full cell constructed by coupling KVP2O7@C cathode with a hard carbon anode can achieve a high operating voltage (3.55 V), high energy density (184 W h kg(-1)) and superior cycling stability (89% capacity retention after 400 cycles). (c) 2021 Published by Elsevier B.V.

Automated summary

The designed and synthesized carbon-matrixed potassium vanadium pyrophosphate powder KVP2O7@C shows promising performance as a cathode material for potassium-ion batteries, with a high reversible capacity, energy density, and potassium storage mechanism revealed. A full cell constructed by coupling KVP2O7@C cathode with a hard carbon anode demonstrates high operating voltage, energy density, and superior cycling stability.