Ion dynamics in solid electrolytes for lithium batteries

Uitz, Marlena; Epp, Viktor; Bottke, Patrick; Wilkening, Martin

doi:10.1007/s10832-017-0071-4

Cited by 91 publications

(116 citation statements)

References 142 publications

(180 reference statements)

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“…Hence, the ions are subjected not to a single but to various dynamic processes being stepwise activated with temperature or running in parallel. To our knowledge, this dynamic performance, although Na + ions are of course larger and therefore perhaps more sluggish than Li + ions, exceeds those of the best Li oxides currently discussed as ceramic electrolytes 2,38 . Considering the electrochemical stability of NZSP-type materials 39 this behaviour clearly opens the field for the development of powerful Na ion solid-state batteries.…”

Section: Introductionmentioning

confidence: 77%

Fast Na ion transport triggered by rapid ion exchange on local length scales

Lunghammer

Prutsch

Breuer

et al. 2018

Sci Rep

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The realization of green and economically friendly energy storage systems needs materials with outstanding properties. Future batteries based on Na as an abundant element take advantage of non-flammable ceramic electrolytes with very high conductivities. Na3Zr2(SiO4)2PO4-type superionic conductors are expected to pave the way for inherently safe and sustainable all-solid-state batteries. So far, only little information has been extracted from spectroscopic measurements to clarify the origins of fast ionic hopping on the atomic length scale. Here we combined broadband conductivity spectroscopy and nuclear magnetic resonance (NMR) relaxation to study Na ion dynamics from the µm to the angstrom length scale. Spin-lattice relaxation NMR revealed a very fast Na ion exchange process in Na3.4Sc0.4Zr1.6(SiO4)2PO4 that is characterized by an unprecedentedly high self-diffusion coefficient of 9 × 10−12 m2s−1 at −10 °C. Thus, well below ambient temperature the Na ions have access to elementary diffusion processes with a mean residence time τNMR of only 2 ns. The underlying asymmetric diffusion-induced NMR rate peak and the corresponding conductivity isotherms measured in the MHz range reveal correlated ionic motion. Obviously, local but extremely rapid Na+ jumps, involving especially the transition sites in Sc-NZSP, trigger long-range ion transport and push ionic conductivity up to 2 mS/cm at room temperature.

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Section: Introductionmentioning

confidence: 77%

Fast Na ion transport triggered by rapid ion exchange on local length scales

Lunghammer

Prutsch

Breuer

et al. 2018

Sci Rep

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“…The two activation energies are linked according to the following relation E a, low-T = (α − 1)E a, high-T . 46 For 3D uncorrelated motion the parameter α equals 2. Correlated motion results in α < 2 and, thus, yields asymmetric NMR rate peaks.…”

Section: Dalton Transactions Papermentioning

confidence: 99%

Mismatch in cation size causes rapid anion dynamics in solid electrolytes: the role of the Arrhenius pre-factor

Breuer

Wilkening

2018

Dalton Trans.

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Crystalline ion conductors exhibiting fast ion dynamics are of utmost importance for the development of, e.g., sensors or rechargeable batteries. In some layer-structured or nanostructured compounds fluorine ions participate in remarkably fast self-diffusion processes. As has been shown earlier, F ion dynamics in nanocrystalline, defect-rich BaF 2 is much higher than that in the coarse-grained counterpart BaF 2 . The thermally metastable fluoride (Ba,Ca)F 2 , which can be prepared by joint high-energy ball milling of the binary fluorides, exhibits even better ion transport properties. While long-range ion dynamics has been studied recently, less information is known about local ion hopping processes to which 19 F nuclear magnetic resonance (NMR) spin-lattice relaxation is sensitive. The present paper aims at understanding ion dynamics in metastable, nanocrystalline (Ba,Ca)F 2 by correlating short-range ion hopping with long-range transport properties. Variable-temperature NMR line shapes clearly indicate fast and slow F spin reservoirs. Surprisingly, from an atomic-scale point of view increased ion dynamics at intermediate values of compo-sition is reflected by increased absolute spin-lattice relaxation rates rather than by a distinct minimum in activation energy. Hence, the pre-factor of the underlying Arrhenius relation, which is determined by the number of mobile spins, the attempt frequency and entropy effects, is identified as the parameter that directly enhances short-range ion dynamics in metastable (Ba,Ca)F 2 . Concerted ion migration could also play an important role to explain the anomalies seen in NMR spin-lattice relaxation.

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“…Considering nanocrystalline ionic conductors [1][2][3][4], a range of studies report on enhanced anion and cation dynamics [5,6]. Structural disorder and defects [7][8][9], lattice mismatch [10][11][12] as well as size effects [13][14][15][16][17], which results in extended space charge regions, are used to explain the properties of nanocrystalline compounds.…”

Section: Introductionmentioning

confidence: 99%

Fluorine Translational Anion Dynamics in Nanocrystalline Ceramics: SrF2-YF3 Solid Solutions

Breuer¹,

Stanje²,

Pregartner³

et al. 2018

Preprint

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Nanostructured materials have already become an integral part of our daily life. In many applications ion mobility decisively affects the performance of, e.g., batteries and sensors. Nanocrystalline ceramics often exhibit enhanced transport properties due to their heterogeneous structure showing crystalline (defect-rich) grains and disordered interfacial regions. In particular, anion conductivity in nonstructural binary fluorides easily exceeds that of their coarse-grained counterparts. To further increase ion dynamics aliovalent substitution is a practical method to influence the number of (i) defect sites and (ii) the charge carrier density. Here, we used high energy-ball milling to incorporate Y 3+ ions into the cubic structure of SrF 2 . As compared to pure nanocrystalline SrF 2 the ionic conductivity of Sr 1−x Y x F 2+x with x = 0.3 increased by 4 orders of magnitude reaching 0.8 × 10 −5 S cm −1 at 450 K. We discuss the effect of YF 3 incorporation on conductivities isotherms determined by both activation energies and Arrhenius pre-factors. The enhancement seen is explained by size mismatch of the cations involved, which are forced to form a cubic crystal structure with extra F anions if x is kept smaller than 0.5.

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Ion dynamics in solid electrolytes for lithium batteries

Cited by 91 publications

References 142 publications

Fast Na ion transport triggered by rapid ion exchange on local length scales

Fast Na ion transport triggered by rapid ion exchange on local length scales

Mismatch in cation size causes rapid anion dynamics in solid electrolytes: the role of the Arrhenius pre-factor

Fluorine Translational Anion Dynamics in Nanocrystalline Ceramics: SrF2-YF3 Solid Solutions

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