Abstract:The interest in alternative
energy sources grows rapidly and demands
improved materials. The cutting-edge investigations focus attention
on the development and optimization of solid electrolytes for advanced
energy storage. Their chemical and structural stability defines both
battery performance and lifetime, yet it is studied poorly even for
well-known superionic conductors such as NASICON-based compounds.
In this work, we studied the Li1.3Al0.3Ti1.7(PO4)3 (LATP) stability toward water.
Corresponding ceramics… Show more
“…Since the beginning of our research activities, the path toward the desired lithium-conductive composite membrane has not been easy as we intended to develop the full-cycle synthesis routine. First, we designed the solid-state synthesis of Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) ceramic of the pure NASICON-type phase with high IC (above 4 ∙ 10 −4 S cm −1 ) but severe sensitivity to moisture that had never been characterized before [ 31 , 32 , 33 ]. From now on, we additionally expected the introduction of the inert matrix to protect the LATP filler from the ambient humidity and preserve its originally high IC.…”
Section: Introductionmentioning
confidence: 99%
“…The entire work was categorized into two parts, where a solid instrumental basis was applied to study the materials, including: X-ray diffraction (XRD), attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). Previously, we showed the instability of LATP toward water led to drastic IC losses, along with structural and morphological changes, mostly due to the elution of lithium ions [ 33 ]. The NAq solvents applied in this study possess twice lower polarity compared to water; the dielectric constants are: water 80.1, DMSO 46.7, DMF 36.7, and NMP 32.2 [ 40 ].…”
Redox flow batteries (RFBs) are a prospective energy storage platform to mitigate the discrepancy between barely adjustable energy production and fluctuating demand. The energy density and affordability of RFBs can be improved significantly through the transition from aqueous systems to non-aqueous (NAq) due to their wider electrochemical stability window and better solubility of active species. However, the NAqRFBs suffer from a lack of effective membranes with high ionic conductivity (IC), selectivity (low permeability), and stability. Here, we for the first time thoroughly analyse the impact of tape-casting solvents (dimethylformamide—DMF; dimethylsulfoxide—DMSO; N-methyl-2-pyrrolidone—NMP) on the properties of the composite Li-conductive membrane (Li1.3Al0.3Ti1.7(PO4)3 filler within poly(vinylidene fluoride) binder—LATP+PVDF). We show that the prolonged exposure of LATP to the studied solvents causes slight morphological, elemental, and intrastructural changes, dropping ceramic’s IC from 3.1 to 1.6–1.9 ∙ 10−4 S cm−1. Depending on the solvent, the final composite membranes exhibit IC of 1.1–1.7 ∙ 10−4 S cm−1 (comparable with solvent-treated ceramics) along with correlating permeability coefficients of 2.7–3.1 ∙ 10−7 cm2 min−1. We expect this study to complement the understanding of how the processes underlying the membrane fabrication impact its functional features and to stimulate further in-depth research of NAqRFB membranes.
“…Since the beginning of our research activities, the path toward the desired lithium-conductive composite membrane has not been easy as we intended to develop the full-cycle synthesis routine. First, we designed the solid-state synthesis of Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) ceramic of the pure NASICON-type phase with high IC (above 4 ∙ 10 −4 S cm −1 ) but severe sensitivity to moisture that had never been characterized before [ 31 , 32 , 33 ]. From now on, we additionally expected the introduction of the inert matrix to protect the LATP filler from the ambient humidity and preserve its originally high IC.…”
Section: Introductionmentioning
confidence: 99%
“…The entire work was categorized into two parts, where a solid instrumental basis was applied to study the materials, including: X-ray diffraction (XRD), attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). Previously, we showed the instability of LATP toward water led to drastic IC losses, along with structural and morphological changes, mostly due to the elution of lithium ions [ 33 ]. The NAq solvents applied in this study possess twice lower polarity compared to water; the dielectric constants are: water 80.1, DMSO 46.7, DMF 36.7, and NMP 32.2 [ 40 ].…”
Redox flow batteries (RFBs) are a prospective energy storage platform to mitigate the discrepancy between barely adjustable energy production and fluctuating demand. The energy density and affordability of RFBs can be improved significantly through the transition from aqueous systems to non-aqueous (NAq) due to their wider electrochemical stability window and better solubility of active species. However, the NAqRFBs suffer from a lack of effective membranes with high ionic conductivity (IC), selectivity (low permeability), and stability. Here, we for the first time thoroughly analyse the impact of tape-casting solvents (dimethylformamide—DMF; dimethylsulfoxide—DMSO; N-methyl-2-pyrrolidone—NMP) on the properties of the composite Li-conductive membrane (Li1.3Al0.3Ti1.7(PO4)3 filler within poly(vinylidene fluoride) binder—LATP+PVDF). We show that the prolonged exposure of LATP to the studied solvents causes slight morphological, elemental, and intrastructural changes, dropping ceramic’s IC from 3.1 to 1.6–1.9 ∙ 10−4 S cm−1. Depending on the solvent, the final composite membranes exhibit IC of 1.1–1.7 ∙ 10−4 S cm−1 (comparable with solvent-treated ceramics) along with correlating permeability coefficients of 2.7–3.1 ∙ 10−7 cm2 min−1. We expect this study to complement the understanding of how the processes underlying the membrane fabrication impact its functional features and to stimulate further in-depth research of NAqRFB membranes.
“…We synthesized the composite membranes used in this work by initially refining the procedures for both the ceramic filler and the polymer film. Here, we focus on the preparation of the PVDF film, as we have described the LATP synthesis elsewhere. , The target polymer film should ideally be thin and possess low porosity and uniform roughness. To identify suitable conditions for membrane preparation, we varied the casting conditions as follows: selecting a suitable solvent → achieving a uniform membrane thickness → cleaning the casting substrate → drying the samples → controlling additional minor variations.…”
Section: Resultsmentioning
confidence: 99%
“…Ceramic pellets of LATP and LAGTP were prepared through a solid-state reaction . Lithium carbonate (Li 2 CO 3 , ≥99%, Sigma-Aldrich), ammonium dihydrogen phosphate (NH 4 H 2 PO 4 , ≥98%, Alfa Aesar), aluminum nitrate (Al(NO 3 ) 3 ·9H 2 O, ≥97%, RusChem), germanium(IV) oxide (GeO 2 , ≥99.99%, Sigma-Aldrich), and titanium(IV) oxide (TiO 2 , ≥99.5%,Sigma-Aldrich) were used for the preparation of LATP and LAGTP powder.…”
Redox flow batteries (RFBs) are a burgeoning electrochemical platform for long-duration energy storage, but present embodiments are too expensive for broad adoption. Nonaqueous redox flow batteries (NAqRFBs) seek to reduce system costs by leveraging the large electrochemical stability window of organic solvents (> 3 V) to operate at high cell voltages and to facilitate the use of redox couples that are incompatible with aqueous electrolytes. However, a key challenge for emerging nonaqueous chemistries is the lack of membranes/separators with suitable combinations of selectivity, conductivity, and stability. Single-ion conducting ceramics, integrated with polymeric fillers to make flexible composites, may offer a pathway to the performance attributes needed for competitive nonaqueous systems. Here, we explore composite polymer-inorganic binder-filler membranes for lithium-based NAqRFBs, investigating two different ceramic compounds with NASICON-type (NASICON: sodium (Na) Super Ionic CONductor) crystal structure, Li1.3Al0.3Ti1.7(PO4)3 (LATP) and Li1.4Al0.4Ge0.2Ti1.4(PO4)3 (LAGTP), blended with a polyvinylidene fluoride (PVDF) polymeric matrix. We characterize the physicochemical and electrochemical properties of the synthesized membranes as a function of processing conditions and formulation using a range of microscopic, spectroscopic, and electrochemical techniques. We then integrate select composite membranes into a single electrolyte flow cell configuration and perform polarization measurements with different redox electrolyte compositions. We find that mechanically robust, chemically stable LATP/PVDF composites can support > 40 mA cm −2 at 400 mV cell overpotential, but further improvements are needed in selectivity. The insights gained through this work begin to establish the foundational knowledge needed to advance composite polymer-inorganic membranes/separators for NAqRFBs.
“…The flexibility of the NASICON structure has also allowed for the development of battery materials containing mobile divalent cations, such as calcium or zinc . Finally, in some recent studies, NASICON compounds have also been examined for applications in unconventional battery architectures, such as seawater or redox-flow batteries …”
Natrium super ionic
conductor (NASICON) compounds form a rich and
highly chemically tunable family of crystalline materials that are
of widespread interest because they include exemplars with high ionic
conductivity, low thermal expansion, and redox tunability. This makes
them suitable candidates for applications ranging from solid-state
batteries to nuclear waste storage materials. The key to an understanding
of these properties, including the origins of effective cation transport
and low, anisotropic (and sometimes negative) thermal expansion, lies
in the lattice dynamics associated with specific details of the crystal
structure. Here we closely examine the prototypical NASICON compound,
NaZr
2
(PO
4
)
3
, and obtain detailed
insights into such behavior via variable-temperature neutron diffraction
and
23
Na and
31
P solid-state NMR studies, coupled
with comprehensive density functional theory-based calculations of
NMR parameters. Temperature-dependent NMR studies yield some surprising
trends in the chemical shifts and the quadrupolar coupling constants
that are not captured by computation unless the underlying vibrational
modes of the crystal are explicitly taken into account. Furthermore,
the trajectories of the sodium, zirconium, and oxygen atoms in our
dynamical simulations show good qualitative agreement with the anisotropic
thermal parameters obtained at higher temperatures by neutron diffraction.
The work presented here widens the utility of NMR crystallography
to include thermal effects as a unique probe of interesting lattice
dynamics in functional materials.
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