Electrochemical Stability of Li6.5La3Zr1.5M0.5O12 (M = Nb or Ta) against Metallic Lithium

Kim, Yunsung; Yoo, Aeri; Schmidt, Robert D.; Sharafi, Asma; Lee, Hee Chul; Wolfenstine, J.; Sakamoto, Jeff

doi:10.3389/fenrg.2016.00020

Cited by 66 publications

(66 citation statements)

References 34 publications

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“…This model indicates an incomplete, first semicircle with a peak at ≈300 kHz that corresponds to grain boundary conduction in the LLZO pellets. [20,36] Symmetric Li||LLZO||Li cells exhibit an additional impedance contribution that is not present for the Au||LLZO||Au cells, which has a peak at ≈1 kHz. [16] To verify this assignment, a separate EIS measurement was carried out from 7 MHz to 250 mHz using symmetric Au||LLZO||Au cells ( Figure S9, Supporting Information), which further revealed the bulk impedance contribution and yielded grain boundary impedance response similar to that observed in Li-Li symmetric cells.…”

Section: Impact Of Reactivity On Interfacial Impedancementioning

confidence: 99%

“…[18] Removing the Li 2 CO 3 / LiOH reaction layer, usually achieved via mechanical polishing, results in significantly lower interfacial impedance; [19] however, little is known about the chemistry or long-term stability of the interface between "pristine" LLZO and Li metal. [20] However, the underlying (electro) chemical mechanisms for this behavior are still unknown. Indeed, there is some evidence that the dopant type affects the long-term stability of LLZO in contact with Li metal.…”

Section: Introductionmentioning

confidence: 99%

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Dopant‐Dependent Stability of Garnet Solid Electrolyte Interfaces with Lithium Metal

Zhu

Connell

Tepavcevic

et al. 2019

Advanced Energy Materials

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materials are a particularly promising class of solid electrolytes for all-solidstate lithium metal batteries, as they are predicted to have a wide electrochemical stability window, [5,6] can be synthesized with very high density (>97%) [7,8] and, through aliovalent doping, can achieve room temperature Li-ion conductivities as high as ≈1.0 mS cm −1 with negligible electronic conductivity. [9] However, significant fundamental issues remain unresolved for garnet-based all-solid-state batteries, including low accessible current densities, [10] the persistence of Li dendrite formation, [11,12] and perhaps most importantly, ambiguities as to whether the interfaces between LLZO and both Li metal [13,14] and high voltage oxide cathodes [15,16] are stable over extended cycling. Indeed, developing deep understanding of the intrinsic reactivity between solid electrolytes and relevant electrode materials is crucial to developing high voltage solidstate batteries with long lifetimes, as the presence of any significant (electro)chemical reactivity will ultimately lead to premature cell failure during extended cycling.Understanding interfacial stability is an especially challenging issue common to all solid-state battery systems due to the inability of many experimental techniques to adequately interrogate the chemical properties of buried interfaces. Such studies are further complicated when one or both materials at the interface are unstable to exposure to air, water, etc., as Li 7 La 3 Zr 2 O 12 (LLZO) garnet-based materials doped with Al, Nb, or Ta to stabilize the Li + -conductive cubic phase are a particularly promising class of solid electrolytes for all-solid-state lithium metal batteries. Understanding of the intrinsic reactivity between solid electrolytes and relevant electrode materials is crucial to developing high voltage solid-state batteries with long lifetimes. Using a novel, surface science-based approach to characterize the intrinsic reactivity of the Li-solid electrolyte interface, it is determined that, surprisingly, some degree of Zr reduction takes place for all three dopant types, with the extent of reduction increasing as Ta < Nb < Al. Significant reduction of Nb also takes place for Nb-doped LLZO, with electrochemical impedance spectroscopy (EIS) of Li||Nb-LLZO||Li symmetric cells further revealing significant increases in impedance with time and suggesting that the Nb reduction propagates into the bulk. Density functional theory (DFT) calculations reveal that Nb-doped material shows a strong preference for Nb dopants toward the interface between LLZO and Li, while Ta does not exhibit a similar preference. EIS and DFT results, coupled with the observed reduction of Zr at the interface, are consistent with the formation of an "oxygen-deficient interphase" (ODI) layer whose structure determines the stability of the LLZO-Li interface.

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Section: Impact Of Reactivity On Interfacial Impedancementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dopant‐Dependent Stability of Garnet Solid Electrolyte Interfaces with Lithium Metal

Zhu

Connell

Tepavcevic

et al. 2019

Advanced Energy Materials

Self Cite

236

282

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“…Partial substitution of the Zr 4+ site in LLZ by other higher valence cations, such as Nb 5+ [13,14], Ta 5+ [15][16][17][18][19][20][21][22][23], W 6+ [24,25], and Mo 6+ [26], is effective at stabilizing the cubic phase, and the conductivity at room temperature is greatly improved to 1 mS cm −1 by controlling the dopants content and optimizing Li + concentration in the garnet framework. Although a solid-state battery with an Nb-doped LLZ as SE has already been demonstrated [13,27,28], a Ta-doped LLZ showed much better chemical stability against a Li metal electrode than when Nb-doped [29,30]. The other dopants, such as W 6+ , Mo 6+ , or Nb 5+ in LLZ, could potentially become a redox center at relatively high potential against Li + /Li [31].…”

Section: Introductionmentioning

confidence: 98%

Formation and Stability of Interface between Garnet-Type Ta-doped Li7La3Zr2O12 Solid Electrolyte and Lithium Metal Electrode

et al. 2018

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Garnet-type Li 7-x La 3 Zr 2-x Ta x O 12 (LLZT) is considered a good candidate for the solid electrolyte in all-solid-state lithium batteries because of its reasonably high conductivity around 10 −3 S cm −1 at room temperature and stability against lithium (Li) metal with the lowest redox potential. In this study, we synthesized LLZT with a tantalum (Ta) content of 0.45 via a conventional solid-state reaction process and constructed a Li/LLZT/Li symmetric cell by attaching Li metal foils on the polished top and bottom surfaces of an LLZT pellet. We investigated the influence of heating temperatures and times on the interfacial charge-transfer resistance between LLZT and the Li metal electrode. In addition, the effect of the interface resistance on the stability for Li deposition and dissolution was examined using a galvanostatic cycling test. The lowest interfacial resistance of 25 Ω cm 2 at room temperature was obtained by heating at 175 • C (5 • C lower than the melting point of Li) for three to five hours. We confirmed that the current density at which the short circuit occurs in the Li/LLZT/Li cell via the propagation of Li dendrite into LLZT increases with decreasing interfacial charge transfer resistance.

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“…Partial substitution of the Zr 4+ site by other higher valence cations, such as Nb 5+ [11,12] and Ta 5+ [13,14,15,16,17,18,19] stabilizes the highly-conductive cubic phase. The conductivity at room temperature for both Ta- and Nb-doped LLZ with optimized Li contents (6.4–6.5) in crystal framework attain up to 1 × 10 −3 S cm −1 , but the former has much higher chemical stability against Li metal electrode than the latter [20,21]. …”

Section: Introductionmentioning

confidence: 99%

“…Although Li-stuffed garnet-type oxide is a good candidate for SE in a solid-state battery, high-temperature sintering at 1000–1200 °C is generally needed for densification [7,11,12,13,14,15,16,17,18,19,20,21] and this temperature is too high to suppress the undesired side reaction between the majority of electrode active materials and SE and the formation of impurity phases [22]. Li + conducting Li 3 BO 3 with a low melting point (~700 °C) has been applied to form the interface between LiCoO 2 and garnet-type SE by a co-sintering process [23,24], but the conductivity for Li 3 BO 3 is low (10 −7 –10 −6 S cm −1 at room temperature) and there are currently limited electrode materials that can be used for solid-state batteries with garnet-type SEs developed by the co-sintering process.…”

Section: Introductionmentioning

confidence: 99%

Properties of Lithium Trivanadate Film Electrodes Formed on Garnet-Type Oxide Solid Electrolyte by Aerosol Deposition

et al. 2018

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We fabricated lithium trivanadate LiV3O8 (LVO) film electrodes for the first time on a garnet-type Ta-doped Li7La3Zr2O12 (LLZT) solid electrolyte using the aerosol deposition (AD) method. Ball-milled LVO powder with sizes in the range of 0.5–2 µm was used as a raw material for LVO film fabrication via impact consolidation at room temperature. LVO film (thickness = 5 µm) formed by AD has a dense structure composed of deformed and fractured LVO particles and pores were not observed at the LVO/LLZT interface. For electrochemical characterization of LVO film electrodes, lithium (Li) metal foil was attached on the other end face of a LLZT pellet to comprise a LVO/LLZT/Li all-solid-state cell. From impedance measurements, the charge transfer resistance at the LVO/LLZT interface is estimated to be around 103 Ω cm2 at room temperature, which is much higher than at the Li/LLZT interface. Reversible charge and discharge reactions in the LVO/LLZT/Li cell were demonstrated and the specific capacities were 100 and 290 mAh g−1 at 50 and 100 °C. Good cycling stability of electrode reaction indicates strong adhesion between the LVO film electrode formed via impact consolidation and LLZT.

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Electrochemical Stability of Li6.5La3Zr1.5M0.5O12 (M = Nb or Ta) against Metallic Lithium

Cited by 66 publications

References 34 publications

Dopant‐Dependent Stability of Garnet Solid Electrolyte Interfaces with Lithium Metal

Dopant‐Dependent Stability of Garnet Solid Electrolyte Interfaces with Lithium Metal

Formation and Stability of Interface between Garnet-Type Ta-doped Li7La3Zr2O12 Solid Electrolyte and Lithium Metal Electrode

Properties of Lithium Trivanadate Film Electrodes Formed on Garnet-Type Oxide Solid Electrolyte by Aerosol Deposition

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