Two <mml:math display="inline"><mml:mrow><mml:msub><mml:mi mathvariant="normal">Li</mml:mi><mml:mrow><mml:mn>1.1</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mi mathvariant="normal">V</mml:mi><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mrow><mml:mn>8</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>Li1.1V3O8 samples prepared by two different routes were investigated: SG350, obtained by firing a sol-gel precursor at <mml:math display="inline"><mml:mrow><mml:mn>350</mml:mn><mml:mo>°</mml:mo><mml:mi mathvariant="normal">C</mml:mi></mml:mrow></mml:math>350°C , and SS580, obtained by solid-state reaction at <mml:math display="inline"><mml:mrow><mml:mn>580</mml:mn><mml:mo>°</mml:mo><mml:mi mathvariant="normal">C</mml:mi></mml:mrow></mml:math>580°C . The electrochemical lithium insertion behaviors were studied and revealed important differences, especially on capacity fading upon lithium cycling. This article is focused on the lithium insertion mechanism in <mml:math display="inline"><mml:mrow><mml:msub><mml:mi mathvariant="normal">Li</mml:mi><mml:mrow><mml:mn>1.1</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mi mathvariant="normal">V</mml:mi><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mrow><mml:mn>8</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>Li1.1V3O8 and on its consequences on cyclability of the materials studied. This study shows that the capacity fading due to the two-phased phenomenon at <mml:math display="inline"><mml:mrow><mml:mn>2.6</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi mathvariant="normal">V</mml:mi></mml:mrow></mml:math>2.6V could be related to an increase of the drastic change in cell lattice constants leading to local damage of the crystal structure. It seems also to depend on the morphology of the compound studied. The dissolution of small quantity of <mml:math display="inline"><mml:msup><mml:mi mathvariant="normal">V</mml:mi><mml:mrow><mml:mn>III</mml:mn></mml:mrow></mml:msup></mml:math>VIII in the electrolyte may occur during the last electrochemical phenomenon at <mml:math display="inline"><mml:mrow><mml:mn>2.35</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi mathvariant="normal">V</mml:mi></mml:mrow></mml:math>2.35V . It is also evidenced that this dissolution depends on the morphology of the compound studied. Discussions are provided on possible mechanisms for the dissolution process and on the relationships between the dissolution reaction and the capacity fading upon cycling.

Two Li_1.1V₃O₈ samples have been prepared by heating a sol–gel precursor at 350 and 650 °C, i.e. below and above the melting point, respectively. Their electrochemical lithium insertion behavior was investigated after different grinding treatments. Important differences were observed, both in initial capacity and in cyclability. Attempts were made to correlate these differences to the material characteristics (composition, morphology and structure). The importance of grain morphology (size, size distribution and shape) and texture (agglomeration of smaller particles or not) has been evidenced. The size and agglomeration of the grains play a major role on the initial capacity, while their crystal shape (well formed crystals or no crystal shape) seems to be the main factor influencing the cyclability. This latter morphology feature was also shown to affect differently the partial capacity fading occurring on each electrochemical Li insertion process.

Due to their fuel flexibility and high efficiency solid oxide cells are a promising technology for sustainable energy production and storage. Nickel in combination with yttria-stabilized zirconia (YSZ) or gadolinium-doped ceria (GDC), forming Ni-YSZ or Ni-GDC cermets respectively, are the most widely adopted electrodes in solid oxide fuel cell fabrication. Currently, there is an increasing interest in cermet electrodes for hydrogen generation through high temperature steam electrolysis using solid oxide electrolysis cells (SOECs). However, durability remains a major issue for reliable operation of SOEC systems. A variety of processes accountable for permanent performance degradation of SOECs has been identified based on post-mortem cell analysis. Besides, transient/reversible degradation processes are typically examined by indirect methods, like impedance spectroscopy. The reason is that the application of material characterization techniques during SOEC operational conditions is challenging. In this work we provide a direct correlation between Ni-YSZ and Ni-GDC electrodes surface oxidation states and their performance during steam electrolysis using operando experimental evidence provided by near ambient pressure X-ray photoelectron and near edge X-ray absorption fine structure spectroscopy. We show that nickel surface oxidation may induce significant performance degradation in Ni-YSZ cathodes, while on the contrary has minor effects in Ni-GDC. Remarkably, we found that in case of Ni-GDC electrodes, small modification of GDC oxidation state can have an important impact on the electrolysis performance. The results highlight the crucial role of the cathode electrode surface oxidation state on the SOEC functionality and have potential implications for the design and operation strategies of more efficient and durable SOEC devices.