Electronic properties of Ir3Li and ultra-nanocrystalline lithium superoxide formation

A New Cathode Material for a Li–O2 Battery Based on Lithium Superoxide

“…Therefore, a reasonable explanation for the new Raman bands is likely due to surface adsorption of oxygen from air to form either chemisorbed oxygen atoms and/or physiosorbed O 2 molecules. The surface-adsorbed oxygen can easily modify the surface structure and symmetry and remove the original doubly degenerate Raman E′ mode. , Previous reported EPR experiments on Ir and LiIr 3 powder under Ar or under oxygen at 100 K showed that O 2 is selectively adsorbed onto Ir sites . Therefore, since Raman is known to be a surface-sensitive technique while XRD and EPR are not, the removal of E′ degeneracy is observed here at ambient temperature.…”

“…30,31 Previous reported EPR experiments on Ir and LiIr 3 powder under Ar or under oxygen at 100 K showed that O 2 is selectively adsorbed onto Ir sites. 10 Therefore, since Raman is known to be a surface-sensitive technique while XRD and EPR are not, the removal of E′ degeneracy is observed here at ambient temperature. Once the two Raman bands are formed, the subsequent spectra are stable for days.…”

“…However, Li–O 2 cells containing these soluble catalysts can experience reduced cycle life due to degradation of the redox mediators via parasitic reactions with electrodes and discharge products . Li–O 2 cells with alternative, more conductive discharge products such as defect-rich Li 2 O 2 or amorphous Li 2 O 2 have been shown to reduce charge overpotentials. , Similarly, cathode materials such as Ir-based materials − that form lithium superoxide (LiO 2 ) during discharge of Li–O 2 batteries have been shown to cycle with low charge overpotentials due to the high electronic conductivity of LiO 2 . , Numerous experimental and theoretical studies have investigated LiO 2 as a component of the discharge product, which was previously thought to exist only as a thermodynamically unstable intermediate. − Zhai et al demonstrated that LiO 2 is formed as part of the discharge products along with Li 2 O 2 on activated carbon electrodes in a LiCF 3 SO 3 -TEGDME electrolyte, where LiO 2 disproportionation occurs under both Ar and O 2 . DFT calculations supported the experimental findings. , …”

Template assisted lithium superoxide growth for lithium–oxygen batteries

“…7 Since LiIr 3 favors the formation of LiO 2 , in another paper we prepared LiIr 3 in bulk through high temperature solid state synthesis. 10 The most intense XRD peak of the high temperature synthesized LiIr 3 is the (121) peak. In the presence of the LiIr 3 cathode, LiO 2 apparently forms exclusively as the discharge product through a “template assisted LiO 2 growth process”.…”

“…In addition, this is the rst time that a TEM image of a LiO 2 aggregate was successfully captured under 80 kV scanning electron beam irradiation while 200 kV irradiation led to decomposition from LiO 2 to Li 2 O. 10 Also another LiIr alloy, LiIr-rGO/GDL, was explored as a cathode in a Li-O 2 cell. The cell ran well with a low over-potential gap of 0.8 V (3.50-2.75 V) and reached 100 cycles at 1000 mA h g −1 capacity with replacement of the Li anode.…”