Smart combination of manifold carbonaceous materials with admirable functionalities (like full of pores/functional groups, high specific surface area) is still a mainstream/preferential way to address knotty issues of polysulfides dissolution/shuttling and poor electrical conductivity for S-based cathodes. However, extensive use of conductive carbon fillers in cell designs/technology would induce electrolytic overconsumption and thereby shelve high-energy-density promise of Li–S cells. To cut down carbon usage, we propose the incorporation of multi-functionalized NiFe2O4 quantum dots (QDs) as affordable additive substitutes. The total carbon content can be greatly curtailed from 26% (in traditional S/C cathodes) to a low/commercial mass ratio (~ 5%). Particularly, note that NiFe2O4 QDs additives own superb chemisorption interactions with soluble Li2Sn molecules and proper catalytic features facilitating polysulfide phase conversions and can also strengthen charge-transfer capability/redox kinetics of overall cathode systems. Benefiting from these intrinsic properties, such hybrid cathodes demonstrate prominent rate behaviors (decent capacity retention with ~ 526 mAh g−1 even at 5 A g−1) and stable cyclic performance in LiNO3-free electrolytes (only ~ 0.08% capacity decay per cycle in 500 cycles at 0.2 A g−1). This work may arouse tremendous research interest in seeking other alternative QDs and offer an economical/more applicable methodology to construct low-carbon-content electrodes for practical usage.
Pyrite FeS2 has long been
a research focus as the alternative
anode of rechargeable Ni–Fe cells owing to its eye-catching
merits of great earth-abundance, attractive electrical conductivity,
and output capacity. However, its further progress is impeded by unsatisfactory
cyclic behaviors due to still “ill-defined” phase changes.
To gain insights into the pyrite working principles/failure factors,
we herein design a core–shell hybrid of a FeS2@carbon
nanoreactor, an optimal anode configuration approaching the practical
usage state. The resultant electrodes exhibit a Max. specific capacity of ∼272.89 mAh g–1 (at
∼0.81 A g–1), remarkably improved cyclic
longevity/stability (beyond ∼80% capacity retention after 103 cycles) and superior rate capability (∼146.18 mAh
g–1 is remained at ∼20.01 A g–1) in contrast to bare FeS2 counterparts. The as-built
Ni–Fe full cells can also output impressive specific energy/power
densities of ∼87.38 Wh kg–1/ ∼ 11.54
kW kg–1. Moreover, a refreshed redox reaction working
mechanism of “FeS2OH ↔FeS2↔Fe0
(in pyrite domains)” is redefined
based
on real-time electrode characterizations at distinct operation stages.
In a total cyclic period, the configured pyrite-based anodes would
stepwise undergo three critical stages nominally named “retention”,
“phase transition/coexistence”, and “degradation”,
each of which is closely related to variations on anodic compositions/structures.
Combined with optimal electrode configurations and in-depth clarifications
on inherent phase conversions, this focus study may guide us to maximize
the utilization efficiency of pyrite for all other aqueous electrochemical
devices.
Fast-response/stable Ni–Bi cells achieved by hollowing-out Bi@carbon nanospheres are an improved electricity storage choice to couple with green energy harvesting.
The advancement of
Ni–Bi batteries has turned sluggish because
of impenetrable barriers related to physicochemical instability of
bismuthic species under thermal conditions. This directly makes Bi-based
anodes impossible to hybridize with graphitic carbons for a longer-term
cyclic lifespan. To break this constraint, we herein propose an effective
strategy by incorporating Fe into bismuthic systems to form multielement
anodes. The smart Bi/Fe merits combination/complementation can drastically
promote the tolerable temperature of Bi-containing nanomaterials over
500 °C, enabling carbon encapsulation without altering their
geometric properties and in the meantime endowing the anodes with
inherited electrochemical superiorities. The as-built BiFeO3@carbon anodes exhibit prominent electrode performances with excellent
electrochemical activity (both Bi- and Fe-based components act as
faradaic redox reaction sites), excellent rate capabilities, and impressive
capacity retention (∼83.4% after 2000 cycles). We further unveil
the anodic phase conversions of “BiFeO3 →
Bi2O3/Fe2O3” (via
the transition state of Bi2O3(222)) based on
the real-time characterizations/post-analysis at distinct cyclic stages.
The packed full cells exhibit max. energy/power densities of ∼90.72
W h kg–1/∼1.3 kW kg–1.
Our study may offer a promising engineering route to promote the development
of safe and applicable Ni–Bi batteries in near-future applications.
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.