Positive Electrode Passivation by Side Discharge Products in Li-O Batteries.

The development of high specific energy Li-O batteries faces a problem of poor cycling as a result of passivation of the positive electrode by both the discharge product (LiO) and side products (LiCO, etc.). The latter are the result of oxidation of the electrode materials or electrolyte components primarily by discharge intermediate superoxide anions (O) and, in less degree, by LiO.

Homogeneous nucleation of LiO under Li-O battery discharge.

The development of high-energy lithium-oxygen batteries has significantly slowed by numerous challenges including capacity limitations due to electrode surface passivation by the discharge product LiO. Since the passivation rate and intensity are dependent on the deposit morphology, herein, we focus on the mechanisms governing LiO formation within the porous cathode. We report evidence of homogeneous nucleation of LiO crystallites and their further assembly in bulk of the electrolyte solution in DMSO, which possesses a high donor number.

Small-angle neutron scattering studies of pore filling in carbon electrodes: mechanisms limiting lithium-air battery capacity.

Many obstacles impede the development of Li-air batteries for practical applications. In particular, there is lack of understanding of the dynamics of processes occurring in porous air electrodes during discharge, including oxygen transport limitations, pore clogging and electrode passivation by both insulating discharge and parasitic reaction products. Here, using small-angle neutron scattering, which provides information on the whole electrode adequate to electrochemical data, we uncover the mechanisms limiting the Li-O2 porous carbon electrode capacity by analysis of the cathode pore filling in highly and poorly solvating media - dimethyl sulfoxide and acetonitrile.

Lithium peroxide crystal clusters as a natural growth feature of discharge products in Li-O2 cells.

The often observed and still unexplained phenomenon of the growth of lithium peroxide crystal clusters during the discharge of Li-O2 cells is likely to happen because of self-assembling Li2O2 platelets that nucleate homogeneously right after the intermediate formation of superoxide ions by a single-electron oxygen reduction reaction (ORR). This feature limits the rechargeability of Li-O2 cells, but at the same time it can be beneficial for both capacity improvement and gain in recharge rate if a proper liquid phase mediator can be found.