Addressing voltage decay in Li-rich cathodes by broadening the gap between metallic and anionic bands

Oxygen release and irreversible cation migration are the main causes of voltage fade in Li-rich transition metal oxide cathode. But their correlation is not very clear and voltage decay is still a bottleneck. Herein, we modulate the oxygen anionic redox chemistry by constructing Li2ZrO3 slabs into Li2MnO3 domain in Li1.21Ni0.28Mn0.51O2, which induces the lattice strain, tunes the chemical environment for redox-active oxygen and enlarges the gap between metallic and anionic bands. This modulation expands the region in which lattice oxygen contributes capacity by oxidation to oxygen holes and relieves the charge transfer from anionic band to antibonding metal–oxygen band under a deep delithiation. This restrains cation reduction, metal–oxygen bond fracture, and the formation of localized O2 molecule, which fundamentally inhibits lattice oxygen escape and cation migration. The modulated cathode demonstrates a low voltage decay rate (0.45 millivolt per cycle) and a long cyclic stability.

Effect Of Annealing On The Behavior Of Oxygen Dissolved In Germanium And Optical Properties Of Single Crystals

<p>The annealing effect in the temperature range from 350 to 450 °С on the behavior of interstitial oxygen О_i dissolved in germanium and on optical properties of single crystals has been investigated by Fourier transformed infrared spectrometry. It was found that oxygen band maximum of 843 cm^–1 shifted toward the 856 cm⁻¹ with oxygen concentration increasing after annealing at the oxygen partial pressure ranged from 1 to 10³ Pа. The annealing at lower values led to the decrease of 843 cm^–1 band intensity due to the formation of thermal donors (TD) on the basis of dissolved oxygen atoms О_i. It was established that TD formation and the decrease of unbound oxygen concentration affected optical properties of the crystals.</p>

Oxygen Impurity in Germanium Single Crystals Determination by Infrared Spectrometry

Oxygen impurity in Germanium single crystals has been characterized using Fourier transformed infrared spectrometry. The crystals were grown by Czochralski method in an argon atmosphere. The oxygen concentration in crystals was determined on optical density from the absorption band at 843 cm−1. It was established that oxygen dissolved concentration in Germanium is variable from 0,2·1016 to 1,3·1016 сm−3. The oxygen band maximum shifts toward 856 cm−1 when its concentration increases under the influence of annealing in the oxygen containing atmosphere with ≤ 10−3 Па.