Structure design enables stable anionic and cationic redox chemistry in a T2-type Li-excess layered oxide cathode.

Coupled with anionic and cationic redox chemistry, Li-rich/excess cathode materials are prospective high-energy-density candidates for the next-generation Li-ion batteries. However, irreversible lattice oxygen loss would exacerbate irreversible transition metal migration, resulting in a drastic voltage decay and capacity degeneration. Herein, a metastable layered Li-excess cathode material, T2-type Li0.72[Li0.12Ni0.36Mn0.52]O2, was developed, in which both oxygen stacking arrangement and Li coordination environment fundamentally differ from that in conventional O3-type layered structures. By means of the reversible Li migration processes and structural evolutions, not only can voltage decay be effectively restrained, but also excellent capacity retention can be achieved upon long-term cycling. Moreover, irreversible/reversible anionic/cationic redox activities have been well assigned and quantified by various in/ex-situ spectroscopic techniques, further clarifying the charge compensation mechanism associated with (de)lithiation. These findings of the novel T2 structure with the enhanced anionic redox stability will provide a new scope for the development of high-energy-density Li-rich cathode materials.

Microscopic photoelectron analysis of single crystalline LiCoO2 particles during the charge-discharge in an all solid-state lithium ion battery.

We report synchrotron-based operando soft X-ray microscopic photoelectron spectroscopy under charge-discharge control of single crystalline LiCoO2 (LCO) particles as an active electrode material for an all solid-state lithium-ion battery (LIB). Photoelectron mapping and the photoelectron spectrum of a selected microscopic region are obtained by a customized operando cell for LIBs. During the charge process, a more effective Li extraction from a side facet of the single crystalline LCO particle than from the central part is observed, which ensures the reliability of the system as an operando microscopic photoelectron analyzer that can track changes in the electronic structure of a selected part of the active particle. Based on these assessments, the no drastic change in the Co 2p XPS spectra during charge-discharge of LCO supports that the charge-polarization may occur at the oxygen side by strong hybridization between Co 3d and O 2p orbitals. The success of tracking the electronic-structure change at each facet of a single crystalline electrode material during charge-discharge is a major step toward the fabrication of innovative active electrode materials for LIBs.

Reaction and degradation mechanism in all-solid-state lithium-air batteries.

The reaction and degradation mechanism in all-solid-state Li-air batteries was investigated to improve the cycling performance. It is suggested that Li2O2 is first produced by the H2O-mediated electrochemical reactions during discharging and Li2CO3 is produced by the following chemical reactions. Disruption of the CNTs and residual discharge products, which cause the capacity degradation during cycling, were observed.

All-solid-state lithium-oxygen battery with high safety in wide ambient temperature range.

There is need to develop high energy storage devices with high safety to satisfy the growing industrial demands. Here, we show the potential to realize such batteries by assembling a lithium-oxygen cell using an inorganic solid electrolyte without any flammable liquid or polymer materials. The lithium-oxygen battery using Li1.575Al0.5Ge1.5(PO4)3 solid electrolyte was examined in the pure oxygen atmosphere from room temperature to 120 °C. The cell works at room temperature and first full discharge capacity of 1420 mAh g(-1) at 10 mA g(-1) (based on the mass of carbon material in the air electrode) was obtained. The charge curve started from 3.0 V, and that the majority of it lay below 4.2 V. The cell also safely works at high temperature over 80 °C with the improved battery performance. Furthermore, fundamental data of the electrochemical performance, such as cyclic voltammogram, cycle performance and rate performance was obtained and this work demonstrated the potential of the all-solid-state lithium-oxygen battery for wide temperature application as a first step.

Fabrication and Performance of All-Solid-State Li-Air Battery with SWCNTs/LAGP Cathode.

The all-solid-state Li-air battery has been fabricated, which is constructed by a lithium foil anode, a NASICON-type solid state electrolyte Li1+xAlyGe2-y(PO4)3 (LAGP) and single-walled carbon nanotubes (SWCNTs)/LAGP nanoparticles composite as air electrode. Its electrochemical performance was investigated in air atmosphere. Particularly, this battery exhibited a larger capacity about 2800 mAh g(-1) for the first cycle, while comparatively the battery with multiwalled carbon nanotubes (MWCNTs)/LAGP as cathode had a capacity of only about 1700 mAh g(-1). Also, the battery with SWCNTs/LAGP showed improved cycling performance with a reversible capacity of 1000 mAh g(-1) at a current density of 200 mA g(-1). Our result demonstrated that the all-solid-state Li-air battery with SWCNTs/LAGP as cathode catalyst has a considerable potential for practical application.

Ru/ITO: a carbon-free cathode for nonaqueous Li-O2 battery.

Ru nanoparticles deposited on a conductive support indium tin oxide (Ru/ITO) were applied as a carbon-free cathode in a nonaqueous Li-O2 battery. The Li-O2 battery with Ru/ITO showed much lower charging overpotentials and better cycling performance at 0.15 mA/cm(2) than those with Super P (SP) and SP loaded with Ru nanoparticles (Ru/SP) as the cathodes. The carbon-free cathode Ru/ITO can effectively reduce formation of Li2CO3 or other Li carbonates in a discharging process, which cannot be completely decomposed upon charging, in comparison with the carbon based cathode. The improved performance of Ru/ITO can be attributed to the superior catalytic activity of Ru nanoparticles toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) and the absence of carbon that has been reported to react with Li2O2 to form Li2CO3.