The role of the reducible dopant in solid electrolyte–lithium metal interfaces

DOI: 10.1021/acs.chemmater.2c00379

Authors: Innes Mcclelland (The University of Sheffield; ISIS Neutron and Muon Source; The Faraday Institution) , Hany El-Shinawi (The Faraday Institution; Mansoura University) , Samuel G. Booth (The University of Manchester; The Faraday Institution) , Anna Regoutz (Imperial College London) , Jasmin Clough (The Faraday Institution; The University of Sheffield) , Sebastian Altus (The Faraday Institution; The University of Sheffield) , Edmund J. Cussen (The Faraday Institution; The University of Sheffield) , Peter J. Baker (ISIS Neutron and Muon Source; The Faraday Institution) , Serena A. Cussen (The University of Sheffield; The Faraday Institution)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemistry Of Materials , VOL 21

State: Published (Approved)
Published: May 2022
Diamond Proposal Number(s): 14239

Abstract: Garnet solid electrolytes, of the form Li7La3Zr2O12 (LLZO), remain an enticing prospect for solid-state batteries owing to their chemical and electrochemical stability in contact with metallic lithium. Dopants, often employed to stabilize the fast ion conducting cubic garnet phase, typically have no effect on the chemical stability of LLZO in contact with Li metal but have been found recently to impact the properties of the Li/garnet interface. For dopants more “reducible” than Zr (e.g., Nb and Ti), contradictory reports of either raised or reduced Li/garnet interfacial resistances have been attributed to the dopant. Here, we investigate the Li/LLZO interface in W-doped Li7La3Zr2O12 (LLZWO) to determine the influence of a “reducible” dopant on the electrochemical properties of the Li/garnet interface. Single-phase LLZWO is synthesized by a new sol–gel approach and densified by spark plasma sintering. Interrogating the resulting Li/LLZWO interface/interphase by impedance, muon spin relaxation and X-ray absorption spectroscopies uncover the significant impact of surface lithiation on electrochemical performance. Upon initial contact, an interfacial reaction occurs between LLZWO and Li metal, leading to the reduction of surface W6+ centers and an initial reduction of the Li/garnet interfacial resistance. Propagation of this surface reaction, driven by the high mobility of Li+ ions through the grain surfaces, thickens the resistive interphases throughout the material and impedes Li+ ion transport between the grains. The resulting high resistance accumulating in the system impedes cycling at high current densities. These insights shed light on the nature of lithiated interfaces in garnet solid electrolytes containing a reducible dopant where high Li+ ion mobility and the reducible nature of the dopant can significantly affect electrochemical performance.

Journal Keywords: Electrical properties; Grain; Interfaces; Lithiation; Materials

Diamond Keywords: Solid-State Batteries (SSB); Batteries

Subject Areas: Materials, Chemistry, Physics


Instruments: B18-Core EXAFS

Other Facilities: EMU at ISIS

Added On: 30/05/2022 08:35

Documents:
acs.chemmater.2c00379.pdf

Discipline Tags:

Surfaces Energy Storage Energy Physics Physical Chemistry Energy Materials Chemistry Materials Science interfaces and thin films

Technical Tags:

Spectroscopy X-ray Absorption Spectroscopy (XAS)