Chloro-free synthesis of LiPF6 using the fluorine-oxygen exchange technique

Oxygen-deficient TiO2-x interlayer enabling Li-rich Mn-based layered oxide cathodes with enhanced reversible capacity and cyclability

The unique anion redox mechanism of Li-rich Mn-based layered oxide (LMLO) cathodes endows them with a higher specific capacity compared with conventional cathodes. However, the irreversible anion redox reactions can cause structural degradation and sluggish electrochemical kinetics in the cathode, resulting in a poor electrochemical performance in the batteries. Thus, to address these issues, a single-sided conductive oxygen-deficient TiO_2-x interlayer was applied on a commercial Celgard separator as a coating layer towards the LMLO cathode. After coating TiO_2-x, the initial coulombic efficiency (ICE) of the cathode increased from 92.1% to 95.8%, the capacity retention improved from 84.2% to 91.7% after 100 cycles, and the rate performance of the cathode was significantly enhanced from 91.3 mA h g^-1 to 203.9 mA h g^-1 at 5C. Operando differential electrochemical mass spectroscopy (DEMS) showed that the coating layer could restrain the release of oxygen in the battery, especially from the initial formation process. The X-ray photoelectron spectroscopy (XPS) results demonstrated that the favorable oxygen absorption by the TiO_2-x interlayer benefitted the suppression of side reactions and cathode structural evolution and favored the formation of a uniform cathode-electrolyte interphase on the LMLO cathode. This work provides an alternative path to address the issue of oxygen release in LMLO cathodes.

All alginate-derived high-performance T-Nb2O5/C//seaweed carbon Li-ion capacitors

Benefitting from the well-matched kinetics and capacity between the counter electrodes and the ion transportability of sodium alginate, the all alginate-derived T-Nb2O5/C//seaweed carbon Li-ion capacitor has excellent electrochemical performance.