In the present study,
an in-depth investigation on the structural
transformation in a mesoporous γ-MnO2 cathode during
electrochemical reaction in a zinc-ion battery (ZIB) has been undertaken.
A combination of in situ Synchrotron XANES and XRD studies reveal
that the tunnel-type parent γ-MnO2 undergoes a structural
transformation to spinel-type Mn(III) phase (ZnMn2O4) and two new intermediary Mn(II) phases, namely, tunnel-type
γ-Zn
x
MnO2 and layered-type
L-Zn
y
MnO2, and that these phases
with multioxidation states coexist after complete electrochemical
Zn-insertion. On successive Zn-deinsertion/extraction, a majority
of these phases with multioxidation states is observed to revert back
to the parent γ-MnO2 phase. The mesoporous γ-MnO2 cathode, prepared by a simple ambient temperature strategy
followed by low-temperature annealing at 200 °C, delivers an
initial discharge capacity of 285 mAh g–1 at 0.05
mA cm–2 with a defined plateau at around 1.25 V
vs Zn/Zn2+. Ex situ HR-TEM studies of the discharged electrode
aided to identify the lattice fringe widths corresponding to the Mn(III)
and Mn(II) phases, and the stoichiometric composition estimated by
ICP analysis appears to be concordant with the in situ findings. Ex
situ XRD studies also confirmed that the same electrochemical reaction
occurred on repeated discharge/charge cycling. Moreover, the present
synthetic strategy offers solutions for developing cost-effective
and environmentally safe nanostructured porous electrodes for cheap
and eco-friendly batteries.
Rechargeable zinc-ion batteries (ZIBs)
with high energy densities
appear promising to meet the increasing demand for safe and sustainable
energy storage devices. However, electrode research on this low-cost
and green system are faced with stiff challenges of identifying materials
that permit divalent ion-intercalation/deintercalation. Herein, we
present layered-type LiV3O8 (LVO) as a prospective
intercalation cathode for zinc-ion batteries (ZIBs) with high storage
capacities. The detailed phase evolution study during Zn intercalation
using electrochemistry, in situ XRD, and simulation techniques reveals
the large presence of a single-phase domain that proceeds via a stoichiometric
ZnLiV3O8 phase to reversible solid–solution
Zn
y
LiV3O8 (y > 1) phase. The unique behavior, which is different
from
the reaction with lithium, contributes to high specific capacities
of 172 mAh g–1 and amounts to 75% retention of the
maximum capacity achieved in 65 cycles with 100% Coulombic efficiency
at a current density of 133 mA g–1. The remarkable
performance makes the development of this low-cost and safe battery
technology very promising, and this study also offers opportunities
to enhance the understanding on electrochemically induced metastable
phases for energy storage applications.
Owing
to their safety and low cost, aqueous rechargeable Zn-ion
batteries (ARZIBs) are currently more feasible for grid-scale applications,
as compared to their alkali counterparts such as lithium- and sodium-ion
batteries (LIBs and SIBs), for both aqueous and nonaqueous systems.
However, the materials used in ARZIBs have a poor rate capability
and inadequate cycle lifespan, serving as a major handicap for long-term
storage applications. Here, we report vanadium-based Na2V6O16·3H2O nanorods employed
as a positive electrode for ARZIBs, which display superior electrochemical
Zn storage properties. A reversible Zn2+-ion (de)intercalation
reaction describing the storage mechanism is revealed using the in
situ synchrotron X-ray diffraction technique. This cathode material
delivers a very high rate capability and high capacity retention of
more than 80% over 1000 cycles, at a current rate of 40C (1C = 361
mA g–1). The battery offers a specific energy of
90 W h kg–1 at a specific power of 15.8 KW kg–1, enlightening the material advantages for an eco-friendly
atmosphere.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.