In recent years, it has been demonstrated that the use of blended cathodes is a convenient method for improving the performance of Lithium ion batteries by exploiting the advantageous properties of the parent materials. Blended cathodes allow the tailoring of cathodes with specific characteristics, often beyond the capabilities of any of the parent materials. While there are many high specific capacity lithium ion cathode materials, most of them lack long term stability for commercial use, for instance, Li₂CuO₂ is a promising material with a theoretical capacity of 490 mAh g^-1; however, it exhibits a large capacity fade [1]. High capacities are only obtained during the first cycle, subsequent cycles presenting large capacity fade mainly due to structural transformations of the orthorhombic Li₂CuO₂ to densely packed layered structure during charging [1]. The present work aims to utilize commercial active materials to stabilize the Li₂CuO₂ phase and inhibit its degradation via blending. The materials chosen for this study are LiFePO₄, LiCoO₂ and LiMn₂O₄ considering their high stability, different structure and different average operation voltages (olivine/3.4 V, layered/3.8 V, spinel/4.1 V respectively) [2]. The blending process carried out in this study is via ball mill, because preliminary results have shown that physical mixing via stirring does not yield important synergic effects between the blended materials. Cycling Li₂CuO₂ at 0.1 C yields an initial capacity of 165 mAh g^-1, with a capacity fade of 55 mAh g^-1 after only ten cycles, while Li₂CuO₂/LiFePO₄ cathode blends exhibit only a 22 mAh g^-1 capacity fade, despite an initial capacity of 120 mAh g^-1. Furthermore Li₂CuO₂/LiCoO₂ cathode blends only present a capacity fade of 6 mAh g^-1 after ten cycles, with an initial capacity of 112 mAh g^-1. Lastly, preliminary results of the Li₂CuO₂/LiMn₂O₄ blends have also shown a slight improvement with respect to cyclability. It is evident that the different structure and average voltage of the secondary active material has a large impact on the capacity fade of the blended cathode, it is of great interest to identify the key parameters which optimize the performance of the blended cathode through further analysis by spectroscopic methods. The authors thank CONACyT project No. 1456 and SECITI project seciti/080/2017 for the financial support.

References:

1 G. Ramos-Sanchez, I. C. Romero-Ibarra, J. Vazquez-Arenas, C. Tapia, N. Aguilar-Eseiza and I. Gonzalez, Solid State Ionics, 2017, 303, 89–96.

2 N. Nitta, F. Wu, J. T. Lee and G. Yushin, Mater. Today, 2015, 18, 252–264.