Chia-Chin Chen

Ge/C nanowires as high-capacity and long-life anode materials for Li-ion batteries.

Germanium-based materials (Ge and GeOx) have recently demonstrated excellent lithium-ion storage ability and are being considered as the most promising candidates to substitute commercial carbon-based anodes of lithium-ion batteries. Nevertheless, practical implementation of Ge-based materials to lithium-ion batteries is greatly hampered by the poor cyclability that resulted from the huge volume variation during lithiation/delithiation processes. Herein, uniform carbon-encapsulated Ge and GeOx nanowires were synthesized by a one-step controlled pyrolysis of organic-inorganic hybrid GeOx/ethylenediamine (GeOx/EDA) nanowires in H2/Ar and Ar atmospheres, respectively. The as-obtained Ge/C and GeOx/C nanowires possess well-defined 0D-in-1D morphology and homogeneous carbon encapsulation, which exhibit excellent Li storage properties including high specific capacities (approximate 1200 and 1000 mA h g(-1) at 0.2C for Ge/C and GeOx/C, respectively). The Ge/C nanowires, in particular, demonstrate superior rate capability with excellent capacity retention and stability (producing high stable discharge capacities of about 770 mA h g(-1) after 500 cycles at 10C), making them promising candidates for future electrodes for high-power Li-ion batteries. The improved electrochemical performance arises from synergistic effects of 0D-in-1D morphology and uniform carbon coating, which could effectively accommodate the huge volume change of Ge/GeOx during cycling and maintain perfect electrical conductivity throughout the electrode.

Synergistic, ultrafast mass storage and removal in artificial mixed conductors

Mixed conductors—single phases that conduct electronically and ionically—enable stoichiometric variations in a material and, therefore, mass storage and redistribution, for example, in battery electrodes. We have considered how such properties may be achieved synergistically in solid two-phase systems, forming artificial mixed conductors. Previously investigated composites suffered from poor kinetics and did not allow for a clear determination of such stoichiometric variations. Here we show, using electrochemical and chemical methods, that a melt-processed composite of the ‘super-ionic’ conductor RbAg4I5 and the electronic conductor graphite exhibits both a remarkable silver excess and a silver deficiency, similar to those found in single-phase mixed conductors, even though such behaviour is not possible in the individual phases. Furthermore, the kinetics of silver uptake and release is very fast. Evaluating the upper limit of the relaxation time set by interfacial ambipolar diffusion reveals chemical diffusion coefficients that are even higher than those achieved for sodium chloride in bulk liquid water. These results could potentially stimulate systematic research into powerful, even mesoscopic, artificial mixed conductors.

Phase evolution in single-crystalline LiFePO4 followed by in situ scanning X-ray microscopy of a micrometre-sized battery

LiFePO₄ is one of the most frequently studied positive electrode materials for lithium-ion batteries during the last years. Nevertheless, there is still an extensive debate on the mechanism of phase transformation. On the one hand this is due to the small energetic differences involved and hence the great sensitivity with respect to parameters such as size and morphology. On the other hand this is due to the lack of in situ observations with appreciable space and time resolution. Here we present scanning transmission X-ray microscopy measurements following in situ the phase boundary propagation within a LiFePO₄ single crystal along the (010) orientation during electrochemical lithiation/delithiation. We follow, on a battery-relevant timescale, the evolution of a two-phase-front on a micrometre scale with a lateral resolution of 30 nm and with minutes of time resolution. The growth pattern is found to be dominated by elastic effects rather than being transport-controlled.

Nanosheets of Earth-Abundant Jarosite as Novel Anodes for High-Rate and Long-Life Lithium-Ion Batteries

Nanosheets of earth-abundant jarosite were fabricated via a facile template-engaged redox coprecipitation strategy at room temperature and employed as novel anode materials for lithium-ion batteries (LIBs) for the first time. These 2D materials exhibit high capacities, excellent rate capability, and prolonged cycling performance. As for KFe3(SO4)2(OH)6 jarosite nanosheets (KNSs), the reversible capacities of above 1300 mAh g(-1) at 100 mA g(-1) and 620 mAh g(-1) after 4000 cycles at a very high current density of 10 A g(-1) were achieved, respectively. Moreover, the resulting 2D nanomaterials retain good structural integrity upon cycling. These results reveal great potential of jarosite nanosheets as low-cost and high-performance anode materials for next-generation LIBs.

Author Correction: Decoupling electron and ion storage and the path from interfacial storage to artificial electrodes

In the version of this Perspective originally published, in the sentence “It is worthy of note that the final LiF-free situation characterized by MnO taking up the holes and the (F– containing) MnO surface taking up the lithium ions is also a subcase of the job-sharing concept23.”, the word ‘holes’ should have been ‘electrons’. This has now been corrected.

Microscopic Dynamics of Li+ in Rutile TiO2 Revealed by 8Li β-Detected Nuclear Magnetic Resonance

Ryan M. L. McFadden,1, 2, ∗ Terry J. Buck,3 Aris Chatzichristos,2, 3 Chia-Chin Chen,4 David L. Cortie,1, 2, 3, † Kim H. Chow,5 Martin H. Dehn,2, 3 Victoria L. Karner,1, 2 Dimitrios Koumoulis,6, ‡ C. D. Philip Levy,7 Chilin Li,8 Iain McKenzie,7, 9 Rotraut Merkle,4 Gerald D. Morris,7 Matthew R. Pearson,7 Zaher Salman,10 Dominik Samuelis,4, § Monika Stachura,7 Jiyu Xiao,1 Joachim Maier,4 Robert F. Kiefl,2, 3, 7 and W. Andrew MacFarlane1, 2, 7, ¶ 1Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada 2Stewart Blusson Quantum Matter Institute, University of British Columbia, 2355 East Mall, Vancouver, BC V6T 1Z4, Canada 3Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada 4Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, 70569 Stuttgart, Germany 5Department of Physics, University of Alberta, 4-181 CCIS, Edmonton, AB T6G 2E1, Canada 6Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive East, Los Angeles, CA 90095, USA 7TRIUMF, 4004 Wesbrook Mall, Vancouver, BC V6T 2A3, Canada 8Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai, P.R. China 200050 9Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada 10Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland (Dated: August 11, 2018)