Fundamental understanding on cyclability behaviors of ammonium vanadate nanoarchitectures as cathode materials for Li-ion batteries: A comparative insight of dual modification of precursor and morphology

Abstract

Development of high-performance Li-ion battery electrodes has emerged as an important issue for satisfying good rate capability and long cycle life during electrochemical lithium (de) intercalation. As cathode materials, vanadium-based compounds are very appealing for energy-storage applications owing to their multiple valence states and coordination geometries. However, they still face bottlenecks such as less stable layered structure and intrinsically low ionic/electronic conductivity. This investigation records on two main parts of new strategic design and electrochemical lithium storage for NH4V4O10 (NHV) cathode nanostructures. NHV structures with diverse motifs (i.e. mat-like sheet, square-sheet microflowers, belt-based microflowers, and nano-belt) were systematically fabricated by tailoring the combined reducing agents (H2C2O4 + KSCN and K2C2O4 + HCl), and its concentrations under controlled hydrothermal protocol. Benefiting from H2C2O4 + KSCN as a mixed precursor in different molar ratios (2,1, 1,1, and 1:2), the electrode materials with various shapes such as mat-like sheet, square-sheet microflowers, belt-based microflowers achieved high specific capacities of 132.02, 162.54 and 172.02 mAh g−1, respectively. From results, the nanobelt-like NHV synthesized by the reducing environment of K2C2O4 + HCl with molar ratio of 1:2 at 180 °C for 24 h delivered an extraordinary discharge capacity of 196.76 mAh g−1 at a current density of 30 mA g−1 in a potential region of 1.8–4.0 V, which reach 87.28 % capacity retention over 50 cycles. However, in the process of using K2C2O4 + HCl, the change in hydrothermal conditions led to a decrease in the storage capacity and cyclability behavior. Such results will potentially help in engineering a novel strategy toward developing electrochemically appropriate constructions, which offer efficient vanadate-based nanostructures via modifying the structure and morphology with improved pathway for rapid electron transfer.