LiSnZr(PO4)3: NASICON-type solid electrolyte with excellent room temperature Li+ conductivity

Pareek, Tanvi; Dwivedi, Sushmita; Singh, Birender; Kumar, Deepu; Kumar, Pradeep; Kumar, Sunil

doi:10.1016/j.jallcom.2018.10.384

“…This change in S⋯Li interaction-strength is then predicted to change the profile of the potential energy surface for lithium diffusion along the c-oriented onedimensional channels, giving a higher barrier to diffusion in Li 10 SnP 2 S 12 than in Li 10 GeP 2 S 12 , thereby explaining the reduced room-temperature ionic conductivity and higher lithiumconduction activation energy observed in experiments. [37][38][39][40] While this solid-electrolyte inductive effect model is chemically intuitive, and potentially explains a number of otherwise anomalous conductivity trends, there has previously been insufficient data to confirm whether this mechanism does indeed produce a significant effect in lithium-ion solid electrolytes, including Li 10 Ge 1−x Sn x P 2 S 12 . To address this issue, we have shows that the predictions of the solid-electrolyte inductive effect model hold even in the absence of the structural changes that accompany Sn-substitution in real materials, suggesting that the inductive effect produces a sufficiently large perturbation to the lithium-ion potential energy profile to be experimentally meaningful, even when decoupled from structural changes to the host-framework.…”

Section: Discussionmentioning

confidence: 99%

“…The solid-electrolyte inductive effect model offers a possible explanation for the otherwise anomalous conductivity trend observed for Li 10 Ge 1−x Sn x P 2 S 12 , as well as for a number of other solid electrolyte families. [37][38][39][40] This model proposes that in Li 10 Ge 1−x Sn x P 2 S 12 the lower electronegativity of Sn compared to Ge causes Sn-S bonds to be weaker and more polar than analogous Ge-S bonds. The increased polarity of these Sn-S bonds corresponds to a larger (more negative) charge density associated with the Sn-bonded S atoms, which in turn causes a stronger Coulombic attraction between these S atoms and nearby Li + cations.…”

Section: Discussionmentioning

confidence: 99%

“…Together with the proposal by Krauskopf et al 35 that an inductive effect might explain the observed lithium conductivity trend in Li 10 MP 2 S 12 , solid-electrolyte inductive effects have been invoked to explain anomalous conductivity trends in a number of other systems, 37 including Na 11 Sn 2 PnS 12 (Pn = P, Sb), 38 Na 3 P 1-x As x S 4 , 39 and LiM 2 (PO 4 ) 3 (M = Zr, Sn). 40 The solidelectrolyte inductive-effect model is founded on simple chemical-bonding concepts, making it an appealing model for explaining these unexpected conductivity trends. Yet there is no direct evidence that such an inductive effect does in fact exist.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Evidence for a Solid-Electrolyte Inductive Effect in Superionic Conductors

Culver¹,

Squires²,

Minafra³

et al. 2020

Preprint

View full text Add to dashboard Cite

Identifying and optimizing highly-conducting lithium-ion solid electrolytes is a critical step towards the realization of commercial all–solid-state lithium-ion batteries. Strategies to enhance ionic conductivities in solid electrolytes typically focus on the effects of modifying their crystal structures or of tuning mobile-ion stoichiometries. A less-explored approach is to modulate the chemical-bonding interactions within a material to promote fast lithium-ion diffusion. Recently, the idea of a solid-electrolyte inductive effect was proposed, whereby changes in bonding within the solid-electrolyte host-framework modify the potential-energy landscape for the mobile ions, resulting in an enhanced ionic conductivity. This concept has since been invoked to explain anomalous conductivity trends in a number of solid electrolytes. Direct evidence for a solid-electrolyte inductive effect, however, is lacking—in part because of the challenge of quantifying changes in local bonding interactions within a solid-electrolyte host-framework. <a></a><a>Here, we consider the evidence for a solid-electrolyte inductive effect in the archetypal superionic lithium-ion conductor Li10Ge1−xSnxP2S12, using Rietveld refinements against high-resolution temperature-dependent neutron-diffraction data, Raman spectroscopy, and density functional theory calculations.</a> Substituting Ge for Sn weakens the {Ge,Sn}–S bonding interactions and increases the charge-density associated with the S2- ions. This charge redistribution modifies the Li+ substructure causing Li+ ions to bind more strongly to the host-framework S anions; which in turn modulates the Li-ion potential-energy surface, increasing local barriers for Li-ion diffusion. Each of these effects is consistent with the predictions of the solid-electrolyte inductive effect model. Density functional theory calculations further predict that this inductive effect occurs even in the absence of changes to the host-framework geometry due to Ge → Sn substitution. These results provide direct evidence in support of a measurable solid-electrolyte inductive effect and demonstrate its application as a practical strategy for tuning ionic conductivities in superionic lithium-ion conductors.

show abstract

“…The solid-electrolyte inductive effect model offers a possible explanation for the otherwise anomalous conductivity trend observed for Li 10 Ge 1−x Sn x P 2 S 12 , as well as for a number of other solid electrolyte families. [37][38][39][40] This model proposes that in Li 10 Ge 1−x Sn x P 2 S 12 the lower electronegativity of Sn compared to Ge causes Sn-S bonds to be weaker and more polar than analogous Ge-S bonds. The increased polarity of these Sn-S bonds corresponds to a larger (more negative) charge density associated with the Sn-bonded S atoms, which in turn causes a stronger Coulombic attraction between these S atoms and nearby Li + cations.…”

Section: Discussionmentioning

confidence: 99%

“…This change in S⋯Li interaction-strength is then predicted to change the profile of the potential energy surface for lithium diffusion along the c-oriented onedimensional channels, giving a higher barrier to diffusion in Li 10 SnP 2 S 12 than in Li 10 GeP 2 S 12 , thereby explaining the reduced room-temperature ionic conductivity and higher lithiumconduction activation energy observed in experiments. [37][38][39][40] While this solid-electrolyte inductive effect model is chemically intuitive, and potentially explains a number of otherwise anomalous conductivity trends, there has previously been insufficient data to confirm whether this mechanism does indeed produce a…”

Section: Discussionmentioning

confidence: 99%

Evidence for a Solid-Electrolyte Inductive Effect in Superionic Conductors

Culver¹,

Squires²,

Minafra³

et al. 2020

Preprint

View full text Add to dashboard Cite

Identifying and optimizing highly-conducting lithium-ion solid electrolytes is a critical step towards the realization of commercial all–solid-state lithium-ion batteries. Strategies to enhance ionic conductivities in solid electrolytes typically focus on the effects of modifying their crystal structures or of tuning mobile-ion stoichiometries. A less-explored approach is to modulate the chemical-bonding interactions within a material to promote fast lithium-ion diffusion. Recently, the idea of a solid-electrolyte inductive effect was proposed, whereby changes in bonding within the solid-electrolyte host-framework modify the potential-energy landscape for the mobile ions, resulting in an enhanced ionic conductivity. This concept has since been invoked to explain anomalous conductivity trends in a number of solid electrolytes. Direct evidence for a solid-electrolyte inductive effect, however, is lacking—in part because of the challenge of quantifying changes in local bonding interactions within a solid-electrolyte host-framework. <a></a><a>Here, we consider the evidence for a solid-electrolyte inductive effect in the archetypal superionic lithium-ion conductor Li10Ge1−xSnxP2S12, using Rietveld refinements against high-resolution temperature-dependent neutron-diffraction data, Raman spectroscopy, and density functional theory calculations.</a> Substituting Ge for Sn weakens the {Ge,Sn}–S bonding interactions and increases the charge-density associated with the S2- ions. This charge redistribution modifies the Li+ substructure causing Li+ ions to bind more strongly to the host-framework S anions; which in turn modulates the Li-ion potential-energy surface, increasing local barriers for Li-ion diffusion. Each of these effects is consistent with the predictions of the solid-electrolyte inductive effect model. Density functional theory calculations further predict that this inductive effect occurs even in the absence of changes to the host-framework geometry due to Ge → Sn substitution. These results provide direct evidence in support of a measurable solid-electrolyte inductive effect and demonstrate its application as a practical strategy for tuning ionic conductivities in superionic lithium-ion conductors.

show abstract