Invited Talks: Transition Metal Oxides - University Blog Service - The ...

The John B. Goodenough Symposium in Materials Science & Engineering –
In Honor of His 90 th Birthday
The University of Texas at Austin, Austin, Texas
October 26-27, 2012
High-Voltage Spinel Cathodes for Lithium-Ion Batteries
Katharine Chemelewski, Eun Sung Lee, Zach Moorhead-Rosenberg, Il Tae Kim, and Arumugam Manthiram
Materials Science and Engineering Program, The University of Texas at Austin
Email: manth@austin.utexas.edu Website: http://www.me.utexas.edu/~manthiram
Abstract Body in Space Below:
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The high-voltage spinel cathode LiMn 1.5 Ni 0.5 O 4 is a promising candidate for large-scale energy storage solutions of
the future. With fast, 3D lithium-ion diffusion pathways and a robust crystal structure, this cathode material is well
suited for implementation in vehicle and grid storage applications. However, widespread adoption has been
hampered by capacity fade particularly at elevated temperatures, which has been attributed to many factors
including aggressive solid-electrolyte interphase (SEI) reaction, cation ordering, site defects resulting in the
formation of Mn 3+ , and the orientation of the crystal planes facing the surface. We present here investigations to
develop a fundamental understanding of the factors that govern the electrochemical properties of LiMn 1.5 Ni 0.5 O 4 , as
well as novel techniques to characterize the materials quantitatively and surface modification to suppress unwanted
side reactions. The solubility of Ni in LiMn 1.5 Ni 0.5 O 4 is dependent on temperature and increases with decreasing
annealing temperature (e.g., 700 o C), eliminating the Li x Ni 1-x O impurity. Additionally, precursor synthesis
conditions including temperature, pH, stir speed, pressure, and annealing conditions affect the morphology and
electrochemical properties of the final cathode material, and the orientation of the crystal planes facing the
electrolyte interface is a critical factor for stabilizing the cathode during high-voltage operation. Also, it is known
that the performance of the undoped LiMn 1.5 Ni 0.5 O 4 spinel is influenced by the Mn 3+ content, and a magnetic method
has been developed, for the first time, to determine quantitatively the Mn 3+ content that agrees closely with the
electrochemical data. Furthermore, the degree of cation ordering could be compared by examining the lithium
insertion reaction below 3 V into the empty 16c sites, which is consistent with the FTIR and electrochemical data.
Finally, surface modification with graphene and AlPO 4 is shown to improve the cyclability and rate capability of
high-voltage spinel cathodes.