Dual-defect modulating potassium anchored NH4V4O10 for stable high-energy aqueous zinc-ion batteries

Aqueous zinc-ion batteries (ZIBs) have been regarded as promising secondary batteries due to their remarkable inherent properties. As a typical layer cathode material with a high specific capacity, ammonium vanadate (NH4V4O10) still suffers from sluggish kinetics and poor electronic conductivity, which results in poor rate performance and short service life. Herein, a co-modulation technique that integrates the anchoring effect of substitutional K+ and the modulating effect of dual defects has been proposed to boost the performance of NH4V4O10 (NVO). Coupled with the theoretical calculation results, it not only buffers the dramatic structural deformation upon zinc storage but also enhances the capacitance-limited capacity and improves the electronic conductivity. Meanwhile, the stable presence of K+ and NH4+ as pillars after long cycles is also confirmed. As a result, the specific capacity of the K+-anchored NVO with high-concentration oxygen defect and proper ammonium defect content (KNVOd-2) is 350.8 mAh/g at 1C with an extraordinary energy density of 303 Wh kg−1. The rate capability of the KNVOd-2 is a 109% increase relative to the as-obtained K+ anchored NVO without dual-defect modulation (KNVOd-1) and remains at least 55% retention after 25-times, and without obvious capacity decay at 5C over 1000 cycles. This work provides insights for using co-modulation chemistry to introduce novel properties in layered-structured materials for high-energy aqueous ZIBs.