10 research outputs found
β-NaVP2O7 as a Superior Electrode Material for Na-Ion Batteries
Herein,
we present a novel β-polymorph of sodium vanadium pyrophosphate NaVP2O7
with the KAlP2O7-type
structure obtained via hydrothermal synthesis and further thermal dehydration
of a hydrophosphate intermediate. β-NaVP2O7 demonstrates attractive electrochemical
behavior as a Na-ion positive electrode (cathode) material with practically achieved
reversible capacity of 104 mAh/g at C/10 current density, average operating
voltage of 3.9 V vs. Na/Na+ and only 0.5% volume change between the charged
and discharged states. Electrode material exhibits excellent C-rate capability
and cycling stability, providing the capacity of 90 mAh/g at 20C
discharge rate and < 1% capacity loss after 100 charge-discharge cycles. At
low voltage region (â1.5 V vs. Na/Na+), β-NaVP2O7
reversibly intercalates additional sodium cations leading to unprecedented overall
Na-ion storage ability exceeding 250 mAh/g within the 1.5 â 4.4 V vs. Na/Na+
voltage region. This material is one of only a few materials that exhibits
reversible sodium ion storage capabilities over such a large potential window. </p
Crystal structures and low-dimensional ferromagnetism of sodium nickel phosphates Na5Ni2(PO4)3¡H2O and Na6Ni2(PO4)3OH
Grain boundaries as a diffusion-limiting factor in lithium-rich NMC cathodes for high-energy lithium-ion batteries
âHydrotriphylitesâ Li1-xFe1+x(PO4)1-y(OH)4y as Cathode Materials for Li-ion Batteries
Lithium iron phosphate LiFePO4
triphylite is now one of the core positive electrode (cathode) materials enabling
the Li-ion battery technology for stationary energy storage applications, which
are important for broad implementation of the renewable energy sources. Despite
the apparent simplicity of its crystal structure and chemical composition,
LiFePO4 is prone to off-stoichiometry and demonstrates rich defect
chemistry owing to variations in the cation content and iron oxidation state,
and to the redistribution of the cations and vacancies over two
crystallographically distinct octahedral sites. The importance of the defects
stems from their impact on the electrochemical performance, particularly on
limiting the capacity and rate capability through blocking the Li ion diffusion
along the channels of the olivine-type LiFePO4 structure. Up to now
the polyanionic (i.e. phosphate) sublattice has been considered idle on this
playground. Here, we demonstrate that under hydrothermal conditions up to 16%
of the phosphate groups can be replaced with hydroxyl groups yielding the Li1-xFe1+x(PO4)1-y(OH)4y
solid solutions, which we term âhydrotriphylitesâ. This substitution has
tremendous effect on the chemical composition and crystal structure of the
lithium iron phosphate causing abundant population of the Li-ion diffusion
channels with the iron cations and off-center Li displacements due to their
tighter bonding to oxygens. These perturbations trigger the formation of an
acentric structure and increase the activation barriers for the Li-ion
diffusion. The âhydrotriphyliteâ-type substitution also affects the magnetic
properties by progressively lowering the NĂŠel temperature. The
off-stoichiometry caused by this substitution critically depends on the overall
concentration of the precursors and reducing agent in the hydrothermal
solutions, placing it among the most important parameters to control the
chemical composition and defect concentration of the LiFePO4-based
cathodes
Chemistry, local molybdenum clustering, and electrochemistry in the <tex>Li_{2+x}Mo_{1-x}O_{3}$</tex> solid solutions
A Critical Assessment of the Therapeutic Potential of Resveratrol Supplements for Treating Mitochondrial Disorders
In human cells, mitochondria provide the largest part of cellular energy in the form of adenosine triphosphate generated by the process of oxidative phosphorylation (OXPHOS). Impaired OXPHOS activity leads to a heterogeneous group of inherited diseases for which therapeutic options today remain very limited. Potential innovative strategies aim to ameliorate mitochondrial function by increasing the total mitochondrial load of tissues and/or to scavenge the excess of reactive oxygen species generated by OXPHOS malfunctioning. In this respect, resveratrol, a compound that conveniently combines mitogenetic with antioxidant activities and, as a bonus, possesses anti-apoptotic properties, has come forward as a promising nutraceutical. We review the scientific evidence gathered so far through experiments in both in vitro and in vivo systems, evaluating the therapeutic effect that resveratrol is expected to generate in mitochondrial patients. The obtained results are encouraging, but clearly show that achieving normalization of OXPHOS function with this strategy alone could prove to be an unattainable goal
The Role of Semilabile Oxygen Atoms for Intercalation Chemistry of the Metal-Ion Battery Polyanion Cathodes
Using
the orthorhombic layered Na<sub>2</sub>FePO<sub>4</sub>F
cathode material as a model system we identify the bonding of the
alkali metal cations to the semilabile oxygen atoms as an important
factor affecting electrochemical activity of alkali cations in polyanion
structures. The semilabile oxygens, bonded to the P and alkali cations,
but not included into the FeO<sub>4</sub>F<sub>2</sub> octahedra,
experience severe undercoordination upon alkali cation deintercalation,
causing an energy penalty for removing the alkali cations located
in the proximity of such semilabile oxygens. Desodiation of Na<sub>2</sub>FePO<sub>4</sub>F proceeds through a two-phase mechanism in
the Na-ion cell with a formation of an intermediate monoclinic Na<sub>1.55</sub>FePO<sub>4</sub>F phase with coupled Na/vacancy and Fe<sup>2+</sup>/Fe<sup>3+</sup> charge ordering at 50% state of charge.
In contrast, desodiation of Na<sub>2</sub>FePO<sub>4</sub>F in the
Li-ion cell demonstrates a sloping charge profile suggesting a solid
solution mechanism without formation of a charge-ordered intermediate
phase. A combination of a comprehensive crystallographic study and
extensive DFT-based calculations demonstrates that the difference
in electrochemical behavior of the alkali cation positions is largely
related to the different number of the nearest neighbor semilabile
oxygen atoms, influencing their desodiation potential and accessibility
for the Na/Li chemical exchange, triggering coupled alkali cationâvacancy
ordering and Fe<sup>2+</sup>/Fe<sup>3+</sup> charge ordering, as well
as switching between the âsolid solutionâ and âtwo-phaseâ
charging mechanistic regimes
The Role of Semilabile Oxygen Atoms for Intercalation Chemistry of the Metal-Ion Battery Polyanion Cathodes
Using
the orthorhombic layered Na<sub>2</sub>FePO<sub>4</sub>F
cathode material as a model system we identify the bonding of the
alkali metal cations to the semilabile oxygen atoms as an important
factor affecting electrochemical activity of alkali cations in polyanion
structures. The semilabile oxygens, bonded to the P and alkali cations,
but not included into the FeO<sub>4</sub>F<sub>2</sub> octahedra,
experience severe undercoordination upon alkali cation deintercalation,
causing an energy penalty for removing the alkali cations located
in the proximity of such semilabile oxygens. Desodiation of Na<sub>2</sub>FePO<sub>4</sub>F proceeds through a two-phase mechanism in
the Na-ion cell with a formation of an intermediate monoclinic Na<sub>1.55</sub>FePO<sub>4</sub>F phase with coupled Na/vacancy and Fe<sup>2+</sup>/Fe<sup>3+</sup> charge ordering at 50% state of charge.
In contrast, desodiation of Na<sub>2</sub>FePO<sub>4</sub>F in the
Li-ion cell demonstrates a sloping charge profile suggesting a solid
solution mechanism without formation of a charge-ordered intermediate
phase. A combination of a comprehensive crystallographic study and
extensive DFT-based calculations demonstrates that the difference
in electrochemical behavior of the alkali cation positions is largely
related to the different number of the nearest neighbor semilabile
oxygen atoms, influencing their desodiation potential and accessibility
for the Na/Li chemical exchange, triggering coupled alkali cationâvacancy
ordering and Fe<sup>2+</sup>/Fe<sup>3+</sup> charge ordering, as well
as switching between the âsolid solutionâ and âtwo-phaseâ
charging mechanistic regimes
The Role of Semilabile Oxygen Atoms for Intercalation Chemistry of the Metal-Ion Battery Polyanion Cathodes
Using
the orthorhombic layered Na<sub>2</sub>FePO<sub>4</sub>F
cathode material as a model system we identify the bonding of the
alkali metal cations to the semilabile oxygen atoms as an important
factor affecting electrochemical activity of alkali cations in polyanion
structures. The semilabile oxygens, bonded to the P and alkali cations,
but not included into the FeO<sub>4</sub>F<sub>2</sub> octahedra,
experience severe undercoordination upon alkali cation deintercalation,
causing an energy penalty for removing the alkali cations located
in the proximity of such semilabile oxygens. Desodiation of Na<sub>2</sub>FePO<sub>4</sub>F proceeds through a two-phase mechanism in
the Na-ion cell with a formation of an intermediate monoclinic Na<sub>1.55</sub>FePO<sub>4</sub>F phase with coupled Na/vacancy and Fe<sup>2+</sup>/Fe<sup>3+</sup> charge ordering at 50% state of charge.
In contrast, desodiation of Na<sub>2</sub>FePO<sub>4</sub>F in the
Li-ion cell demonstrates a sloping charge profile suggesting a solid
solution mechanism without formation of a charge-ordered intermediate
phase. A combination of a comprehensive crystallographic study and
extensive DFT-based calculations demonstrates that the difference
in electrochemical behavior of the alkali cation positions is largely
related to the different number of the nearest neighbor semilabile
oxygen atoms, influencing their desodiation potential and accessibility
for the Na/Li chemical exchange, triggering coupled alkali cationâvacancy
ordering and Fe<sup>2+</sup>/Fe<sup>3+</sup> charge ordering, as well
as switching between the âsolid solutionâ and âtwo-phaseâ
charging mechanistic regimes