High capacity monoclinic Nb₂O₅ and semiconducting NbO₂ composite as high-power anode material for Li-Ion batteries

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>Niobium pentoxide, Nb<SUB>2</SUB>O<SUB>5</SUB>, is an intercalation-type material with a high theoretical capacity of ∼404 mAh g<SUP>−1</SUP> for Li-ion batteries. However, electrochemical properties of Nb<SUB>2</SUB>O<SUB>5</SUB> largely depend on its various polymorphs with different crystal structures, and their low electrical conductivity acts as the main obstacle. Here, we report high-temperature calcined monoclinic Nb<SUB>2</SUB>O<SUB>5</SUB> and semiconducting NbO<SUB>2</SUB> composite as a high-power anode material. Monoclinic Nb<SUB>2</SUB>O<SUB>5</SUB> itself as a main active material shows a high capacity of ∼280 mAh g<SUP>−1</SUP>, and NbO<SUB>2</SUB> with a small band gap of ∼0.5 eV not only improves electrical conductivity but also gives a capacity of ∼110 mAh g<SUP>−1</SUP>. To have a synergic effect of these two materials, the Nb<SUB>2</SUB>O<SUB>5</SUB>/NbO<SUB>2</SUB> composite is prepared <I>via</I> simple post-calcination of as-prepared Nb<SUB>2</SUB>O<SUB>5</SUB> under a reduction atmosphere. It shows a discharge capacity of ∼214 mAh g<SUP>−1</SUP> at 0.05 C, a high initial Coulombic efficiency of 94.7%, a superior rate capability of ∼40 mAh g<SUP>−1</SUP> at 100 C, and a robust cycle performance of 81% retention over 900 cycles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Monoclinic Nb<SUB>2</SUB>O<SUB>5</SUB> was prepared by high calcination at 1100 °C. </LI> <LI> Semi-conducting NbO<SUB>2</SUB> was introduced to Nb<SUB>2</SUB>O<SUB>5</SUB> by thermal reduction process. </LI> <LI> Nb<SUB>2</SUB>O<SUB>5</SUB>/NbO<SUB>2</SUB> composite shows a cycle performance of 81% retention over 900 cycles. </LI> <LI> Nb<SUB>2</SUB>O<SUB>5</SUB>/NbO<SUB>2</SUB> composite shows a superior rate capability at 100C. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>