ИСТИНА

Efficient energy storage is of high demand for different applications such as consumer electronics and pure electric vehicles. Lithium-air batteries (LAB) are the most prominent solution due to their high specific energy and huge capacity exceeding that of lithium-ion batteries by an order of magnitude [1]. Typically, LAB consists of lithium metal anode, Li+ conductive electrolyte and oxygen exposed porous cathode. During the discharge Li reduces oxygen to form main product Li2O2. The lack of cycleability of the LAB with carbon positive electrode is associated with Li2CO3 byproduct formation that occurs during battery discharge due to superoxide species attacking carbon material [2,3]. Among alternative materials different highly conductive carbides and nitrides are considered. Recently it was reported that TiC-based positive electrode exhibits better stability than carbon and reversible formation/decomposition of Li2O2 [4], but the underlying mechanisms are still uncovered. Here we report a NAPXPS study of the electrochemical and chemical processes at the surface of TiC in an all-solid-state cell [3] with TiC positive electrode under operando conditions. NAP XPS was applied to the operating electrochemical cells, that allowed us to observe oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) and to determine their intermediates and products formed on TiC upon discharge and recharge under oxygen pressures up to 0.1 mbar. The working electrode is composed of 50 nm nanoparticles of TiC deposited on Ti-free solid glass-ceramic NASICON-type electrolyte. Metallic Li foil was used as a counter electrode.. We observed that TiС is oxidized during discharge [4]. This process is accompanied by the formation of sp2 –like carbon, with its nature being unclear. In addition, using open circuit regime to separate chemical and electrochemical reactions we found lithium carbonate at the TiC surface. This indicates that TiC electrode most probably is also unstable under long-term operation of the Li-air battery.