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HQ - US Army Development of High Voltage Olivine Cathode

Monday, 2 October 2017: 11:50
Maryland C (Gaylord National Resort and Convention Center)
J. L. Allen, S. A. Delp, J. Wolfenstine, T. R. Jow (U.S. Army Research Laboratory), D. Liu, C. S. Kim, M. Cho, A. Guerfi, and K. Zaghib (Research Institute of Hydro-Quebec (IREQ))
The need for environmentally friendly, safe, stable, and low cost materials for application in lithium-ion batteries has led to strong interest in developing olivine-type LiMPO4 (M = Fe, Mn, Co, Ni) cathode materials. Among them, LiFePO4 (LFP) has been extensively studied and commercialized. However, LFP has some special shortcomings in practical applications, such as low potential plateau (3.4 V vs. Li/Li+) and small packing density (due to the inclusion of large-volume carbon), which lead to relatively low specific energy density (580 Wh kg-1). Whereas LiCoPO4 (LCP) in the olivine family has been considered as an attractive cathode candidate due to the large theoretical capacity (167 mAh g-1), high operating voltage (4.8 V vs. Li/Li+) and high specific energy density (800 Wh kg-1).

However, LCP suffers from severe capacity fade due to the low intrinsic electronic/ionic conductivity, structure deterioration and electrolyte decomposition [1]. In this work, Hydro Quebec and US Army Research Laboratory dedicated to develop the high voltage olivine cathode. Specifically, partially Co-substitution strategy with a carbon coating was successfully used to improve the cycling stability of LCP cathode [2]. FIG. 1 shows the cyclability of substituted-LCP olivine cathode at room temperature under C/3 rate, from which no obvious capacity loss was observed in 100 cycles. Moreover, phosphate based cathodes may provide higher abuse tolerance than oxides at a given voltage due the strong covalent band of P-O. Therefore, the substituted high voltage LCP olivine cathode has the apparent potential to be a next decade success story in lithium-ion technologies and to find large application in the next generation lithium-ion batteries.

References

[1] K. Tadanaga, F. Mizuno, A. Hayashi, T. Minami, M. Tatsumisago, Electrochemistry 71, 1192 (2003).

[2] J. L. Allen, J. L. Allen, T. Thompson, S. A. Delp, J. Wolfenstine, T. Richard Jow, J. Power Sources, 327, 229 (2016).