Solid Electrolytes: Extremely Fast Charge Carriers in Garnet‐Type Li6La3ZrTaO12 Single Crystals

The development of all-solid-state electrochemical energy storage systems, such as lithium-ion batteries with solid electrolytes, requires stable, electronically insulating compounds with exceptionally high ionic conductivities. Considering ceramic oxides, garnet-type Li7La3Zr2O12 and derivatives, see Zr-exchanged Li6La3ZrTaO12 (LLZTO), have attracted great attention due to its high Li+ ionic conductivity of 10−3 S cm−1 at ambient temperature. Despite numerous studies focussing on conductivities of powder samples, only few use time-domain NMR methods to probe Li ion diffusion parameters in single crystals. Here we report on temperature-variable NMR relaxometry measurements using both laboratory and spin-lock techniques to probe Li jump rates covering a dynamic time window spanning several decades. Both techniques revealed a consistent picture of correlated Li ion jump diffusion in the single crystal; the data perfectly mirror a modified BPP-type relaxation response being based on a Lorentzian-shaped relaxation function. The rates measured could be parameterized with a single set of diffusion parameters. Results from NMR are completely in line with ion transport parameters derived from conductivity spectroscopy.

[1]  Wolfgang G. Zeier,et al.  Direct Observation of the Interfacial Instability of the Fast Ionic Conductor Li10GeP2S12 at the Lithium Metal Anode , 2016 .

[2]  Prateek Mehta,et al.  Effects of Sublattice Symmetry and Frustration on Ionic Transport in Garnet Solid Electrolytes. , 2016, Physical review letters.

[3]  P. Heitjans,et al.  Heterogeneous lithium diffusion in nanocrystalline Li2O:Al2O3 composites , 2003 .

[4]  Yizhou Zhu,et al.  Origin of Outstanding Stability in the Lithium Solid Electrolyte Materials: Insights from Thermodynamic Analyses Based on First-Principles Calculations. , 2015, ACS applied materials & interfaces.

[5]  Philippe Knauth,et al.  Inorganic solid Li ion conductors: An overview , 2009 .

[6]  P. Heitjans,et al.  7Li NMR relaxation by diffusion in hexagonal and cubic LixTiS2 , 1994 .

[7]  E. Purcell,et al.  Relaxation Effects in Nuclear Magnetic Resonance Absorption , 1948 .

[8]  Venkataraman Thangadurai,et al.  Garnet-type solid-state fast Li ion conductors for Li batteries: critical review. , 2014, Chemical Society reviews.

[9]  I. Letofsky-Papst,et al.  Order vs. disorder — a huge increase in ionic conductivity of nanocrystalline LiAlO2 embedded in an amorphous-like matrix of lithium aluminate , 2014 .

[10]  Satoshi Hori,et al.  High-power all-solid-state batteries using sulfide superionic conductors , 2016, Nature Energy.

[11]  Peter Lamp,et al.  Inorganic Solid-State Electrolytes for Lithium Batteries: Mechanisms and Properties Governing Ion Conduction. , 2015, Chemical reviews.

[12]  J. Sann,et al.  Impedance spectroscopic study of the charge transfer resistance at the interface between a LiNi0.5Mn1.5O4 high-voltage cathode film and a LiNbO3 coating film , 2016 .

[13]  M. Wilkening,et al.  Fast Li ion dynamics in the solid electrolyte Li7 P3 S11 as probed by (6,7) Li NMR spin-lattice relaxation. , 2015, Chemphyschem : a European journal of chemical physics and physical chemistry.

[14]  Fuminori Mizuno,et al.  Solid-State Lithium-Ion Batteries for Electric Vehicles , 2014 .

[15]  Q. Ma,et al.  Separating bulk from grain boundary Li ion conductivity in the sol–gel prepared solid electrolyte Li1.5Al0.5Ti1.5(PO4)3 , 2015 .

[16]  P. Bottke,et al.  Ion Dynamics in Solid Electrolytes: NMR Reveals the Elementary Steps of Li+ Hopping in the Garnet Li6.5La3Zr1.75Mo0.25O12 , 2015 .

[17]  Jürgen Janek,et al.  A solid future for battery development , 2016, Nature Energy.

[18]  Yizhou Zhu,et al.  First principles study on electrochemical and chemical stability of solid electrolyte–electrode interfaces in all-solid-state Li-ion batteries , 2016 .

[19]  Alexander Kuhn,et al.  Structure and dynamics of the fast lithium ion conductor "Li7La3Zr2O12". , 2011, Physical chemistry chemical physics : PCCP.

[20]  M. Wilkening,et al.  Highly Mobile Ions: Low-Temperature NMR Directly Probes Extremely Fast Li+ Hopping in Argyrodite-Type Li6PS5Br , 2013 .

[21]  M. Wilkening,et al.  Long-range Li+ dynamics in the lithium argyrodite Li7PSe6 as probed by rotating-frame spin-lattice relaxation NMR. , 2013, Physical chemistry chemical physics : PCCP.

[22]  K. Funke,et al.  Jump relaxation in solid electrolytes , 1993 .

[23]  Venkataraman Thangadurai,et al.  Fast Lithium Ion Conduction in Garnet‐Type Li7La3Zr2O12 , 2007 .

[24]  V. Thangadurai,et al.  Li self-diffusion in garnet-type Li7La3Zr2O12as probed directly by diffusion-inducedLi7spin-lattice relaxation NMR spectroscopy , 2011 .

[25]  Gerbrand Ceder,et al.  Interface Stability in Solid-State Batteries , 2016 .

[26]  Norihito Kijima,et al.  Synthesis and structure analysis of tetragonal Li7La3Zr2O12 with the garnet-related type structure , 2009 .

[27]  M. Wilkening,et al.  Crystal Structure of Garnet-Related Li-Ion Conductor Li7–3xGaxLa3Zr2O12: Fast Li-Ion Conduction Caused by a Different Cubic Modification? , 2016, Chemistry of materials : a publication of the American Chemical Society.

[28]  Jeffrey W. Fergus,et al.  Ceramic and polymeric solid electrolytes for lithium-ion batteries , 2010 .

[29]  M. Wilkening,et al.  Site Occupation of Ga and Al in Stabilized Cubic Li7–3(x+y)GaxAlyLa3Zr2O12 Garnets As Deduced from 27Al and 71Ga MAS NMR at Ultrahigh Magnetic Fields , 2015 .

[30]  K. Schwarz,et al.  DFT Study of the Role of Al3+ in the Fast Ion-Conductor Li7–3xAl3+xLa3Zr2O12 Garnet , 2014, Chemistry of materials : a publication of the American Chemical Society.

[31]  Ashok Kumar Baral,et al.  Fast Solid-State Li Ion Conducting Garnet-Type Structure Metal Oxides for Energy Storage. , 2015, The journal of physical chemistry letters.

[32]  P. Heitjans,et al.  Tuning the Li diffusivity of poor ionic conductors by mechanical treatment: High Li conductivity of strongly defective LiTaO3 nanoparticles , 2008 .

[33]  M. Wilkening,et al.  High‐Energy Mechanical Treatment Boosts Ion Transport in Nanocrystalline Li2B4O7 , 2016 .

[34]  P. Bottke,et al.  Correlated fluorine diffusion and ionic conduction in the nanocrystalline F(-) solid electrolyte Ba(0.6)La(0.4)F(2.4)-(19)F T1(ρ) NMR relaxation vs. conductivity measurements. , 2014, Physical chemistry chemical physics : PCCP.