Dominik Samuelis

Porous LiMn2O4 as cathode material with high power and excellent cycling for aqueous rechargeable lithium batteries

A porous LiMn2O4 consisting of nano grains was prepared by using polystyrene as template. It was studied as a cathode material for aqueous rechargeable lithium batteries (ARLBs) using 0.5 mol l−1Li2SO4 aqueous solution as the electrolyte. Charge and discharge capacities at a current density of 10 A g−1 (about 90C) were 76% and 95% of the total capacity (118 mAh g−1), respectively. The power density can be up to 10000 W kg−1 and the cycling behavior is excellent. After 10000 cycles at 9C with 100% DOD (depth of discharge), the capacity retention of porous LiMn2O4 is 93%, which indicates that it can be used for a lifetime without maintenance. The main reasons for its excellent electrochemical performance are due to the nano grains, porous morphology and high crystalline structure. In addition, the acid-free aqueous electrolyte prevents Mn2+ from dissolution. These excellent results suggest a great promise for the development of aqueous rechargeable lithium batteries (ARLBs) in practical application.

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.

Charge carrier accumulation in lithium fluoride thin films due to Li-ion absorption by titania (100) subsurface.

The thermodynamically required redistribution of ions at given interfaces is being paid increased attention. The present investigation of the contact LiF/TiO(2) offers a highly worthwhile example, as the redistribution processes can be predicted and verified. It consists in Li ion transfer from LiF into the space charge zones of TiO(2). We not only can measure the resulting increase of lithium vacancy conductivity in LiF, we also observe a transition from n- to p-type conductivity in TiO(2) in consistency with the generalized space charge model.

β-NMR of 8Li+ in rutile TiO2

We report preliminary low-energy β-NMR measurements of 8Li+ implanted in single crystal rutile TiO2 at an applied field of 6.55 T and 300 K. We observe a broad 12 kHz wide quadrupole split resonance with unresolved features and a sharp component at the Larmor frequency. The line broadening may be caused by overlapping multi-quantum transitions or motion of 8Li+ on the scale of its lifetime (1.21 s). We also find spin-lattice relaxation that is relatively fast compared to other wide band gap insulators. The origin of this fast relaxation is also likely quadrupolar and may be due to anisotropic 8Li+ diffusion.

LiFePO4: From an Insulator to a Robust Cathode Material

Ортофосфаты LiFe0,9M0,1PO4 со структурой оливина, допированные ванадием и титаном, были получены с помощью механохимически стимулированного твердофазного синтеза с использованием высокоэнергетической планетарной мельницы АГО-2 и последующего отжига при 750 °C. Показано, что ионы V и Ti не полностью замещают ионы Fe2+ в структуре LiFePO4. Оставшаяся часть этих ионов участвует в образовании второй фазы с насиконоподобной структурой: моноклинной Li3V2(PO4)3 (пространственная группа P21/n) и ромбоэдрической LiTi2(PO4)3 (пространственная группа R-3c). Согласно ПЭМ, средний размер частиц нанокомпозитов около 100–300 нм. ЭДС микроанализ показал, что мелкие частицы вторичных фаз сегрегированы на поверхности более крупных частиц LiFePO4. На зарядно-разрядных кривых LiFe0,9M0,1PO4 присутствуют плато, соответствующие LiFePO4 и второй фазе. Допирование ванадием повышает устойчивость циклирования LiFePO4 и улучшает его циклируемость при высоких скоростях в большей степени, чем в случае допирования титаном.

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)