3 years ago

Electrochemical In Situ Formation of a Stable Ti-Based Skeleton for Improved Li-Storage Properties: A Case Study of Porous CoTiO3 Nanofibers

Electrochemical In Situ Formation of a Stable Ti-Based Skeleton for Improved Li-Storage Properties: A Case Study of Porous CoTiO3 Nanofibers
Si-Yu Liu, Xing-Long Wu, Jing-Ping Zhang, Han-Chi Wang, Chao-Ying Fan
Bimetallic transition-metal oxides, which exhibit superior electrochemical properties compared with pristine single-metal oxides, have recently become a topic of significant research interest for applications in lithium-ion batteries (LIBs). Herein, we report a simple and scalable electrospinning method to synthesize porous CoTiO3 nanofibers as the precursor for nanostructured bimetallic transition-metal oxides formed electrochemically in situ. This strategy ensures uniform mixing and perfect contact between two constituent transition-metal oxides during the lithiation/delithiation process. Furthermore, CoTiO3 nanofibers based on ultrafine CoTiO3 nanocrystals are interconnected to form a nano/microstructured 3D network, which ensures the high stability of the in situ formed structure composed of bimetallic transition-metal oxides, and also fast ion/electron transfer and electrolyte penetration into the electrode. Electrochemical measurements revealed the excellent lithium storage (647 mAh g−1 at 0.1 Ag−1) and retention properties (600 mAh g−1 at 1 Ag−1 after 1200 cycles) of the CoO/TiO2 electrode. Moreover, the electrochemical reaction mechanism was explored by using ex situ X-ray photoelectric spectroscopy and cyclic voltammetry tests, which confirmed the two-phase reaction processes in the electrodes. These results clearly validate the potential of CoTiO3 with a unique nano/microstructured morphology as the precursor for a bimetallic transition-metal oxide for use as the anode material for long-life LIBs. Anodes go bimetallic: On cycling of as-prepared 3D CoTiO3 nanofibers, during the first lithiation process, along with the formation of a Li2O matrix, TiIV and CoII species were converted/reduced to LixTiO2 nanoparticles (NPs) and metallic Co NPs, respectively, which suggested the electrochemical in situ formation of bimetallic transition-metal oxides (see figure).

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/chem.201700984

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