A new
approach is employed to boost the electrochemical kinetics and stability
of vanadium oxygen hydrate (VOH, V2O5·nH2O) employed for aqueous zinc-ion battery (ZIB)
cathodes. The methodology is based on electrically conductive polyaniline
(PANI) intercalated–exfoliated VOH, achieved by preintercalation
of an aniline monomer and its in situ polymerization
within the oxide interlayers. The resulting graphene-like PANI–VOH
nanosheets possess a greatly boosted reaction-controlled contribution
to the total charge storage capacity, resulting in more material undergoing
the reversible V5+ to V3+ redox reaction. The
PANI–VOH electrode obtains an impressive capacity of 323 mAh
g–1 at 1 A g–1, and state-of-the-art
cycling stability at 80% capacity retention after 800 cycles. Because
of the facile redox kinetics, the PANI–VOH ZIB obtains uniquely
promising specific energy–specific power combinations: an energy
of 216 Wh kg–1 is achieved at 252 W kg–1, while 150 Wh kg–1 is achieved at 3900 W kg–1. Electrochemical impedance spectroscopy (EIS) and
galvanostatic intermittent titration technique (GITT) analyses indicate
that with PANI–VOH nanosheets, there is a simultaneous decrease
in the charge transfer resistance and a boost in the diffusion coefficient
of Zn2+ (by a factor of 10–100) vs the VOH baseline. The strategy of employing PANI for combined intercalation–exfoliation
may provide a broadly applicable approach for improving the performance
in a range of oxide-based energy storage materials.
A stable lean‐electrolyte operating lithium–sulfur (Li–S) battery based on a cathode of Li2S in situ electrocatalytically deposited from L2S8 catholyte onto a support of metallic molybdenum disulfide (1T‐MoS2) on carbon cloth (CC) is created. The 1T‐MoS2 significantly accelerates the conversion Li2S8 catholyte to Li2S, chemically adsorbs lithium polysulfide (LiPSs) from solution, and suppresses crossover of the LiPSs to the anode. These experimental findings are explained by density functional theory calculations that show that 1T‐MoS2 gives rise to strong adsorption of polysulfides on its surface and is electrocatalytic for the targeted reversible Li–S conversion reactions. The CC/1T‐MoS2 electrode in a Li–S battery delivers an initial capacity of 1238 mAh g−1, with a low capacity fade of only 0.051% per cycle over 500 cycles at 0.5 C. Even at a high sulfur loading (4.4 mg cm−2) and low electrolyte/S (E/S) ratio of 3.7 µL mg−1, the battery achieves an initial reversible capacity of 1176 mA h g−1 at 0.5 C, with 87% capacity retention after 160 cycles. The post 500 cycles Li metal opposing 1T‐MoS2 is substantially smoother than the Li opposing CC, with XPS supporting the role of 1T‐MoS2 in inhibiting LiPSs crossover.
Layered
tin monosulfide (SnS) is a promising anode material for
sodium-ion batteries because of its high theoretical capacity of 1020
mA h g–1. Its large interlayer spacing permits fast
sodium-ion transport, making it a viable candidate for sodium-ion
capacitors (SICs). In this work, we designed and synthesized oriented
SnS nanosheets confined in graphene in the presence of poly(diallyl
dimethyl ammonium chloride) by electrostatic self-assembly during
hydrothermal growth. SnS nanosheets growing along (l00) and (0l0) directions are suppressed because
of the confinement by graphene, which exhibit smaller thickness and
particle size. These nanostructures expose abundant open edges because
of the presence of Sn4+–O, which offers rich active
sites and Na+ easy transport pathways. Vacancies formed
at these edges along with S and N codopants in the graphitic structure
synergistically promoted Na+ surface adsorption/desorption.
Such nanocomposites with SnS nanosheets confined by N,S codoped graphene
demonstrated significantly enhanced pseudocapacitance. The SICs delivered
excellent energy densities of 113 and 54 W h kg–1 at power densities of 101 and 11 100 W kg–1, respectively, with 76% capacity retention after 2000 cycles at
1 A g–1.
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