Nanostructured LiMnPO4 Matrix as Flexible High-rate Cathode Materials

Feng Jiao

Center for Catalytic Science & Technology, Department of Chemical Engineering, University of Delaware, Newark, DE, 19716 USA. Fax: +1-302-831-1048; Tel: +1-302-831-3679; E-mail: jiao@udel.edu

Electronic systems that can cover large areas on flexible substrates have received increasing attention in the past few years, because they enable classes of applications that lie outside those easily-addressed with wafer-based electronics1-3. As the critical component for flexible electronics, a flexible energy storage device is crucial because all the functionalities onboard rely on the power supply. The performance of the current generation is greatly limited by the electrode materials, and many efforts have been devoted to development of high performance flexible batteries4-7. Recently, compliant materials on curvilinear surfaces, such as carbon nanotubes8, carbon nanofibers9, graphene10, metal oxide-based nanowires11, and slurry-type mixtures of nanostructured active materials12, have been explored as flexible battery electrodes. However, these studies have mainly focused on anode electrode materials, and there has been very limited progress on cathode materials for flexible batteries. It is critical to explore cathode electrode materials with the potential to couple with the developed flexible anodes for device applications.
One-dimensional (1D) electrode materials have attracted much attention recently because of their potential application in flexible battery technology. Many 1D anode materials based on carbon and metal oxides have been synthesized for flexible batteries, but only limited studies on the cathode side have been conducted. In this talk, we will present the synthesis of high-rate cathode electrodes based on Mg-modified LiMnPO4 nanofibers. The nanofibers are embedded inside a nanostructured conducting carbon matrix to enhance their electronic conductivity and structural integrity while retaining flexibility. As a result, a 50% increase in capacity is obtained, achieving an outstanding performance of 135 mAh g-1 at a C/10 rate (15 mA g-1). This nanostructured Mg- modified LiMnPO4 matrix also exhibited superior rate capability and much better cycleability compared to its LiMnPO4 counterpart. Even at a high charge/discharge rate of 5C (750 mA g-1),
80% of the capacity (107 mAh g-1) is still retained, representing, to the best of our knowledge, the best rate performance for LiMnPO4 -based electrodes. More importantly, such a superior rate capability is achieved with an excellent cycleability (no capacity fading for 200 deep cycles).

Reference:

1. Lu, Q., Hutchings, G. S., Zhou, Y., Xin, H., Zheng, H., & Jiao, F. Nanostructured flexible Mg- modified LiMnPO4 matrix as high-rate cathode materials for Li-ion batteries. J. Mater. Chem. A,

2014, 2, 6368-6373.