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Modification of High Potential, High Capacity Li2FeP2O7 Cathode Material for Lithium Ion Batteries Jiajia Tan1 and Ashutosh Tiwari1 1 Nanomaterials Research Laboratory, Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112, U.S.A. ABSTRACT Li2FeP2O7 is a newly developed polyanionic cathode material for high performance lithium ion batteries. It is considered very attractive due to its large specific capacity, good thermal and chemical stability, and environmental benignity. However, the application of Li2FeP2O7 is limited by its low ionic and electronic conductivities. To overcome the above problem, a solution-based technique was successfully developed to synthesize Li2FeP2O7 powders with very fine and uniform particle size (< 1 µm), achieving much faster kinetics. The obtained Li2FeP2O7 powders were tested in lithium ion batteries by measurements of cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge cycling. We found that the modified Li2FeP2O7 cathode could maintain a relatively high capacity even at fast discharge rates. INTRODUCTION Lithium ion batteries (LIBs) are widely used as power sources in portable computers, entertainment devices, telecommunications, and recently electrical automobiles. As required by EV (electrical vehicles) and HEV (hybrid electrical vehicles), LIBs should be able to store and release large amount of energy in a short time length, while of light-weight. Therefore, largescale production of novel cathode materials, with high voltage and large specific capacity, were urgently demanded. Currently available cathode materials such as LiCoO2 [1] and LiFePO4 [2] couldn’t fulfill these requirements very well, mostly limited by high price and relatively low specific capacity. A lot of research has been conducted on polyanionic cathode materials. One way of increasing specific capacity is to increase the redox potential of the polyanionic LiMXO4 (M: transition metal; X = P, As, Si, Ge) [3-6]. Though there has been a large amount of work done on this topic, the overall performance of these materials is not significantly greater than that of more traditional cathode materials. Another way of achieving high specific capacity is to increase the number of removable lithium atoms in one formula. For this purpose, extensive studies have been focused on LixM’2 (YO4)3 (x > 1, M’: transition metal; Y: S, P, Mo), leading to the development of Li2FeP2O7 [7]. Although Li2FeP2O7 (LFPO) has low electronic and ionic conductivity, it has a theoretical capacity of 220 mAh/g with both lithium atoms extracted, even higher than that of Li3V2(PO4)3 which can remove three lithium atoms. [8-10] Therefore, it is desirable to synthesize LFPO with improved kinetic properties. In this paper, we are reporting the modification of LFPO synthesized through a solutionbased technique. The effect of synthesis parameters on the crystal structure, morphology and electrochemical performance of the LFPO powders was thoroughly studied.

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