MOF‐Derived MnV₂O₄/C Microparticles with Graphene Coating Anchored on Graphite Sheets: Oxygen Defect Engaged High Performance Aqueous Zinc‐Ion Battery

Abstract

By annealing [Mn(phen)H2O][V2O6] (phen = 1,10‐phenanthroline) in the presence of graphite template, MnV2O4 /C microparticles are obtained, in which MnV2O4 particles with one‐layer or few‐layer coating of graphene are anchored on the graphite sheets. The optimal sample, MnV2O4(p)/C‐700 with a high carbon content (35.3 at. %) can deliver a large specific capacity of 410 mAh g−1 at 0.1 A g−1 with a high capacity retention of 94.3% over 1000 discharge/charge cycles at 20 A g−1 as cathode in zinc‐ion battery. Ex situ X‐ray diffraction, scanning electron microscopy, energy‐dispersive X‐ray spectra, as well as elemental mappings and X‐ray photoelectron spectroscopy of MnV2O4(p)/C‐700 discern the partial phase transformation mechanism of MnV2O4→Zn3(OH)2V2O7(H2O)2 during discharge/charge process. It is because the rich oxygen defects of MnV2O4 can improve electrical conductivity, favor the electron transfer from V→Mn/O, thus facilitate the binding of Zn2+, and the captured Zn2+ cannot be extracted, as evidenced by density functional theory calculations. Furthermore, it is found that O‐deficiency can capture the water shell from the hydrated Zn2+, then the dehydrated Zn2+ is easy to insert into MnV2O4 with lower migration barrier of Zn2+ (0.84 eV), leading to the structural reversibility of MnV2O4 in cycling test.

Coordination polymer-derived Al3+-doped V2O3/C with rich oxygen vacancies for an advanced aqueous zinc-ion battery with ultrahigh rate capability

“…44,46,47 With the intercalation of H + during the 2 nd discharge process, the concentration of OH − in the aqueous solution is excessive, which can combine with Zn x (CF 3 SO 3 ) y from the electrolyte solution to form insoluble Zn x (CF 3 SO 3 ) y (OH) 2 x-y · n H 2 O on the outer surface of the electrode. 46–48 The expectation can be proved by the ex situ EDS results. As shown in Fig.…”

Layered porous Mn0.18V2O5@C with manganese and carbon provided by a metal–organic framework precursor as a cathode material for aqueous zinc-ion batteries

“…Furthermore, the amount of the O-defect is 21.04% in the fully charge state and decreases to 16.34% when deeply discharged to 0.3 V, which is due to the detachment of Zn 2+ /water during the process of charge and discharge. 57 Fig. 6c shows the XPS of V in the MVO@C electrode.…”

Three-dimensional graphene/metal–organic framework composites for electrochemical energy storage and conversion

“…, porous carbon and metal compounds) have been widely used in the field of electrochemistry. 10–14 However, their low conductivity and poor stability limit their further practical applications to a great extent. 15,16 So far, many efforts have been made to solve these problems.…”

“…[5][6][7][8][9] Because of their large surface area, high porosity and unique photoelectric effect, MOFs and their derivatives (i.e., porous carbon and metal compounds) have been widely used in the field of electrochemistry. [10][11][12][13][14] However, their low conductivity and poor stability limit their further practical applications to a great extent. 15,16 So far, many efforts have been made to solve these problems.…”