Instantaneous Surface Li3_{3}PO4_{4} Coating and Al–Ti Doping and Their Effect on the Performance of LiNi0.5_{0.5}Mn1.5_{1.5}O4_{4} Cathode Materials

Using hydrogen peroxide (H2O2), a novel approach was applied for the synthesis of LiNi0.5Mn1.5O4 (LNMO) coated with Li3PO4 and doped with Al3+ and Ti4+ ions. The reaction between LNMO and H2O2 resulted in particles with a partially damaged surface. If the same reaction is done in the presence of lithium, aluminum, titanium, and phosphate ingredients, then all particle facets are intact and show no sign of destruction. It appears that the H2O2 decomposition activates the LNMO surface, generating perfect conditions for the homogeneous deposition of the Li, Al, Ti, and phosphate ions. Electrochemical investigations show a very slow fading process during the cycling, and even after more than 500 cycles, the obtained cathode material shows a high specific capacity of 127 mAh g–1 (at 1 C) (∼98% capacity retention) and an excellent Coulombic efficiency (99.5%)

Charakterisierung von Graphitelektroden für Lithium-Ionen-Akkumulatoren mittels OsO₄ Exposition, XPS und REM

Graphitelektroden sind immer noch fester Bestandteil von kommerziellen Lithium-Ionen-Akku-mulatoren. In der vorliegenden Arbeit wurden Untersuchungsmethoden für die Charakterisierung von Graphitelektroden adaptiert und weiterentwickelt. So wurde die Auswirkung einer OsO₄ Expo-nierung auf Batteriematerialien und auf zyklierte Graphitelektroden systematisch mit der Röntgen-photo-elektronenspektroskopie (XPS) sowie der Rasterelektronenmikroskopie (REM) untersucht. So konnte mit der OsO₄ Exposition ein kontrastverstärkendes Verfahren für die Rasterelektronenmikro-skopie entwickelt werden, mit dem die elektrochemisch aktive Oberfläche von kohlenstoffbasierten Elektroden abgebildet und berechnet werden kann. Weiterhin konnte durch eine OsO₄ Exposition die „solid electrolyte interphase“ (SEI) soweit stabilisiert werden, dass eine Abbildung und Charakterisie-rung im Rasterelektronenmikroskop (REM) mit Rückstreuelektronen möglich wurde. Zu den wichtigen Bestandteilen der Graphitelektroden gehören Binder und Leitruß. Um deren Vertei-lung in Graphitelektroden berechnen und abbilden zu können, wurde ein auf der Rasterelektronenmikroskopie basierendes Messverfahren ausgearbeitet und für die Charakterisierung unterschiedlich getrockneter Graphitelektroden genutzt

Influence of electronically conductive additives on the cycling performance of argyrodite-based all-solid-state batteries

All-solid-state batteries (SSBs) are attracting widespread attention as next-generation energy storage devices, potentially offering increased power and energy densities and better safety than liquid electrolyte-based Li-ion batteries. Significant research efforts are currently underway to develop stable and high-performance bulk-type SSB cells by optimizing the cathode microstructure and composition, among others. Electronically conductive additives in the positive electrode may have a positive or negative impact on cyclability. Herein, it is shown that for high-loading (pelletized) SSB cells using both a size- and surface-tailored Ni-rich layered oxide cathode material and a lithium thiophosphate solid electrolyte, the cycling performance is best when low-surface-area carbon black is introduced

Delithiation/relithiation process of LiCoMnO4\mathrm{LiCoMnO_{4}} spinel as 5 V electrode material

In this work, the LiCoMnO$_{4}$ spinel has been synthesized by a two-step sol-gel based method, followed by sintering at temperatures up to 750 °C in oxygen. After structural characterization of the pristine material via synchrotron and neutron diffraction, the material was characterized via SEM and 6Li-MAS-NMR spectroscopy. $^6$ Li-MAS-NMR spectroscopy in different states of charge revealed, that manganese and cobalt are distributed homogenously throughout the material and the delithiation primary occurs from the manganese environments. It was also shown, that it is not possible to fully delithiate the material in a practical voltage range of an electrolyte. Electrochemical cycling results reveal that about 70% of the lithium can be extracted and reinserted electrochemically in the voltage window from 4.5 to 5.4 V against lithium from/into LiCoMnO$_{4}$. In situ synchrotron powder diffraction results show that lithium extraction/insertion occurs via a single-phase mechanism over the whole range of lithium contents and that the discharge capacity is mainly restricted by the voltage-window of the electrolyte. Furthermore it was shown, that the delithiation occurs up to a potential of 5.6 V

Lithium-air battery cathode modification via an unconventional thermal method employing borax

A novel, unconventional thermal treatment employing borax for preparing porous carbon materials is presented. The new method was used to prepare carbon felt electrodes for use in lithium-air batteries. The etching of the carbon fiber surface was found to be highly controllable by the amount of borax. The resulting felts were characterized by cyclic voltammetry (CV), secondary electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). The borax treatment resulted in a change of the size, shape and orientation of the Li2O2 crystals formed during discharge. © 2016 The Royal Society of Chemistry