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Computational identification and experimental realisation of lithium vacancy introduction into the olivine LiMgPO4

DOI: 10.1021/cm504518q DOI Help

Authors: Leopoldo Enciso Maldonado (University of Liverpool) , Matthew S. Dyer (University of Liverpool) , Michael D. Jones (University of Liverpool) , Ming Li (University of Liverpool) , Julia Payne (University of Liverpool) , Michael J. Pitcher (University of Liverpool) , Mona K. Omir (University of Liverpool) , John Claridge (University of Liverpool) , Frederic Blanc (University of Liverpool) , Matthew Rosseinsky (University of Liverpool)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemistry of Materials , VOL 27 (6)

State: Published (Approved)
Published: February 2015
Diamond Proposal Number(s): 9282

Abstract: Calculation of the energetics of aliovalent substitution into the olivine LiMgPO4 suggests that replacement of Mg2+ by In3+ is the most effective way to introduce lithium vacancies and thus generate lithium ion conductivity. Experimental synthesis accesses materials with up to 17% Li vacancy content. An order of magnitude increase in the high temperature hopping rates probed by 7 Li NMR spin lattice relaxation, and over two orders of magnitude increase in the room temperature Li+ ion conductivity measured by impedance spectroscopy is observed on introduction of In3+ ions and Li vacancies. NMR spectroscopy and calculations reveal that the energy barrier to site-to-site hopping is 0.3 eV – 0.5 eV, comparable with best-in-class non-oxide systems such as argyrodite, but NMR derived hopping rates, and impedance spectroscopy shows that longer range transport is less facile with activation energies in the range of 0.7 – 1 eV. Calculations suggest that this is because the Li vacancies are strongly bound to the In3+ dopants, suggesting that high lithium mobilities in oxides are accessible but high conductivities require strategies to separate defect from dopant.

Subject Areas: Chemistry, Materials

Instruments: I11-High Resolution Powder Diffraction

Other Facilities: ISIS

Added On: 17/02/2015 09:07

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