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Lithium nickelate is a promising electrode material for lithium-ion batteries, however, its low thermal stability is a problem that should be solved. We studied the thermal stability of delithiated lithium nickelate compounds in the presence of electrolyte solvents/solutions. We measured the exothermal heat generation of the reaction system using differential scanning calorimetry. We examined simple systems such as ethylene carbonate with Li 0.2 NiO 2 , using hermetically sealed pans that allowed us to perform the experiments under constant mass conditions. The data were quantitatively analyzed to propose possible reaction mechanisms for the exothermal behavior. We attributed the main source of the exothermal heat to organic solvent combustion caused by oxygen released from the nickelate. We studied similar reactions using other solvents/solutions and electrochemically or chemically delithiated nickelate samples. We also examined the behavior of lithium cobaltate for comparison. We discuss the effect of partial substitution for nickel on thermal stability.Lithium nickelate is an attractive positive electrode material for lithium-ion batteries because of its comparatively low cost and large capacity. 1-3 However, its stability must be improved to meet safety standards, because highly delithiated compounds Li x NiO 2 (xϹ0.3) decompose exothermally at around 200°C. 4-6 It has recently been reported that there is even greater exothermal heat generation when the nickelate material is heated in the presence of organic electrolyte solutions. 7-15 However, the origin of this large heat generation has remained unclear because of the complexity of the reaction system, which contains many components such as electrode material, electrolyte solute, and mixed organic solvents. For examining such thermal behavior, differential scanning calorimetry ͑DSC͒ has been widely used. 5-17 As DSC shows the amount of generated heat quantitatively, a study of simple reaction systems, for example, oxide with a single solvent, may be the key to discovering the reaction mechanism.In this study we report the thermal behavior of Li x NiO 2 in contact with electrolyte solutions using DSC coupled with thermogravimetry ͑TG͒. We examined reactions involving ethylene carbonate ͑EC͒ in particular detail, because EC is often used as the main component in electrolyte solutions. We tested both electrochemically and chemically delithiated compounds and compared their behavior with that of lithium cobaltate. We also discuss the effect of partial substitution for nickel on the thermal stability of the delithiated material. ExperimentalWe prepared nearly stoichiometric LiNiO 2 samples by heating a mixture of LiOH•H 2 O, LiNO 3 , and Ni͑OH͒ 2 ͑1:1:1 in molar ratios͒ in air at 500°C for 6 h and then at 700°C for 24 h. We removed unreacted lithium compounds by washing the heated product with distilled water. The structural and electrochemical characteristics of this compound are detailed elsewhere. 18 We used LiCoO 2 powder ͑Nippon Chemical Industrial͒ as rece...

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A ruthenium-catalyzed hydrovinylation-type cross-coupling of ynamides and ethylene proceeds via ruthenacyclopentene to give 2-aminobuta-1,3-diene derivatives in a highly regioselective manner. It was also demonstrated that 2-aminobuta-1,3-diene derivatives reacted with various dienophiles or singlet oxygen to give a cyclic enamide derivative.