Unveiling the Reaction Mechanism of Metal Oxide Based Anode Materials with High Abnormal Capacity for Lithium-Ion Batteries By Using Synchrotron X-Ray Techniques
Authors: Kim Hyunchul , Balasubramanian Mahalingam , Yoo Jaeseung , Lee Wontae , Yoon Jaesang , Kim JI Man , Yoon Won-Sub 
Published: February 2020

Graphitic carbon is extensively used as anode material in most of the commercial lithium-ion batteries due to its low cost and high coulombic efficiency. However, capacity of carbon anode (372mAh/g and 830mAh/mL) is limited by the reversible electrochemical intercalation of lithium ions in its structure. So, alternative research directions and different anode materials are currently being investigated with an aim to achieve high capacity and cycling stability. Recently, nano-material research has shed light on many high performing materials. Among these, metal oxide based materials such as SnO2, MoO2, Co(OH)2 have been recognized as one of the potential candidates for anode material of lithium–ion batteries because of its higher specific lithium storage capacity [1, 2, 3]. But, their poor capacity retention over long-term charge-discharge cycling due to low electrical conductivity has prevented its use as commercial anode material in lithium-ion batteries. Furthermore, during the electrochemical cycling, metal oxides typically break into small metal clusters, resulting in a large volume expansion and a loss of capacity [4]. For improving the performance of metal oxide based materials, nanostructured materials have received much attention as battery electrodes due to the short transport lengths for both electrons and Li ions, higher electrode-electrode contact area, and better accommodation of the strain of Li insertion/extraction [5]. Although there have been reports in the electrochemical behavior and performance improvement on metal oxide based anode materials for lithium ion batteries, it is still difficult to prove the reaction mechanism and abnormal capacity clearly. For accurate explanation of reaction mechanism and abnormal capacity, it is important to analyze each region systematically.

Herein, we successfully synthesized nano-structured metal oxide materials through simple synthetic strategy. This research also included its novel reaction mechanism during electrochemical cycling with lithium. Structure and electrochemical properties of synthesized material were studied by diverse electrochemical tests, combination of the synchrotron radiation XRD and XAS techniques. Especially, the changes in the local structures during cycling were investigated systematically on the basis of XAS analysis. Based on these results, novel reaction mechanism about the nano-structured metal oxide based anode material during electrochemical cycling was suggested specifically. This finding will not only be helpful in a more complete understanding of the reaction mechanism of  metal oxide based anode materials but also will offer valuable guidance for developing new anode materials with abnormal high capacity for next generation rechargeable batteries. More detailed discussion will be presented at the time of meeting.

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