• Journal of the Korean Electrochemical Society
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• v.23 no.4
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• pp.105-112
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• 2020

Transition metal oxide, which undergoes a conversion reaction in the negative electrode material for a lithium-ion batteries, has a high specific capacity, but still has several critical problems. In this study, manganese pyrophosphate (Mn₂P₂O₇), nickel pyrophosphate (Ni₂P₂O₇), and carbon composite materials with pyrophosphates as novel negative electrode materials instead of transition metal oxide, are synthesized through simple solid-state reaction. The initial reversible capacity of Mn₂P₂O₇ and Ni₂P₂O₇ are 333 and 340 mAh g^-1, and when the composite materials are composed with carbon, the reversible capacity increases to 433 and 387 mAh g^-1, respectively. The initial Coulombic efficiency is also improved by about 10%. The Mn₂P₂O₇ and carbon composite material has the highest initial capacity and efficiency, and has the best cycle performance. Mn₂P₂O₇ containing polyanion, has a lower specific capacity due to the large mass of polyanion compared to MnO (manganese oxide). However, since Mn₂P₂O₇ shows a voltage curve with a slope, the charging (lithiation) voltage increases from 0.51 to 0.57 V (vs. Li/Li⁺), and the discharge (delithiation) voltage decreases from 1.15 to 1.01 V (vs. Li/Li⁺). Therefore, the voltage efficiency of the cell is improved because the voltage difference between charging and discharging is greatly reduced from 0.64 to 0.44 V, and the operating voltage of the full cell increases because the negative electrode potential is lowered during the discharging process.

• Korean Journal of Pharmacognosy
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• v.37 no.1 s.144
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• pp.60-66
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• 2006

Norditerpene alkaloids are the main toxic principles of traditional oriental herb 'chuawu(bu-shi),' which have been used in Chinese materia medica mainly for the treatment of musculoskeletal disorders. They are biosynthesized via cyclization of geranylgeranyl pyrophosphate, incoration of 2-aminoethanol and decarboxylation not via amino acid pathway, and the structural characteristics have tempted several oxidative reactions. In this study various norditerpene alkaloids were subjected to react active manganese dioxide and oxoammonium salt as oxidants. The oxidation was proceeded as dealkylation with aconitine type and dehydrogenations with lycoctonin and heteratisine type.