Special seminar on Friday

Mon Mar 9 11:59:29 CET 2015

CONDENSED MATTER AND
STATISTICAL PHYSICS SECTION

SPECIAL SEMINAR

Friday, 13 March -    11:00 a.m.

Luigi Stasi Seminar Room -    ICTP Leonardo Building   (first floor)

Kunio TAKAYANAGI    ( Tokyo Institute of Technology & JST-CREST- Tokyo)

"Transport of Lithium ions in a LiMn2O4 Nanowire Cathode of a nano Lithium Ion Battery"

Abstract

Structural phase transition of electrode materials in lithium ion batteries (LIBs) during charge-discharge processes results in capacity decrease, and it shorten the LIB life.  In order to avoid capacity decrease, we developed a nano lithium ion battery with a single LiMn2O4 nanowire as a positive electrode, and electronic and structural behavior were studied in-situ in a sub-50pm resolution electron microscope. The LiMn2O4 (LMO) nanowire electrode contacts with ionic liquid electrolyte (ILE) and LTO used as the negative electrode. The LMO nanowires had, in average, lengths of 0.1~0.2mm and diameters of 100nm~200nm. The nanowire electrode is free standing, being suspended between Pt and ILE.

The nanowire battery showed no capacity degradation at high charge/discharge rate (fully charged within 20 minutes) from the first charge/discharge cycle, and structure of LMO transformed reversibly while the cyclic voltammetry between 3.5 – 5.5 V (Li/Li+). The structure of the nanowire at the area of ILE/LMO contact showed cubic to tetragonal phase transformation. The other part of the nanowire showed non-equilibrium structure with a density fluctuation. In the charge/discharge process 80% of the lithium ions are transferred from the LMO nanowire and returned to it reversible, although non-equilibrium distribution of the charge density of Lithium ions along the nanowire. The dynamic of lithium ion transport at high charging rate (large potential difference) should be understood.

References:

1. S. Lee, et al., J. Phys. Chem. C 117, 24236 (2013).

2. S. Lee et al, DOI: 10.1021/nn505952k (2014).