Nanoscale Morphological and Chemical Changes of High Voltage Lithium–Manganese Rich NMC Composite Cathodes with Cycling

Yang, F and Liu, Y and Martha, Surendra Kumar and Wu, Z and Andrews, J C and Ice, G E and Pianetta, P and Nanda, J (2014) Nanoscale Morphological and Chemical Changes of High Voltage Lithium–Manganese Rich NMC Composite Cathodes with Cycling. Nano Letters, 14 (8). pp. 4334-4341. ISSN 1530-6984

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Abstract

Understanding the evolution of chemical composition and morphology of battery materials during electrochemical cycling is fundamental to extending battery cycle life and ensuring safety. This is particularly true for the much debated high energy density (high voltage) lithium–manganese rich cathode material of composition Li1 + xM1 – xO2 (M = Mn, Co, Ni). In this study we combine full-field transmission X-ray microscopy (TXM) with X-ray absorption near edge structure (XANES) to spatially resolve changes in chemical phase, oxidation state, and morphology within a high voltage cathode having nominal composition Li1.2Mn0.525Ni0.175Co0.1O2. Nanoscale microscopy with chemical/elemental sensitivity provides direct quantitative visualization of the cathode, and insights into failure. Single-pixel (∼30 nm) TXM XANES revealed changes in Mn chemistry with cycling, possibly to a spinel conformation and likely including some Mn(II), starting at the particle surface and proceeding inward. Morphological analysis of the particles revealed, with high resolution and statistical sampling, that the majority of particles adopted nonspherical shapes after 200 cycles. Multiple-energy tomography showed a more homogeneous association of transition metals in the pristine particle, which segregate significantly with cycling. Depletion of transition metals at the cathode surface occurs after just one cycle, likely driven by electrochemical reactions at the surface.

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IITH Creators:

IITH Creators	ORCiD
Martha, Surendra Kumar	UNSPECIFIED

Item Type:

Article

Additional Information:

The authors gratefully thank Dr. Michael F. Toney, Dr. Apurva Mehta, and Dr. Johanna Nelson Weker (all from SLAC National Accelerator Laboratory) for valuable discussions. This research at Oak Ridge National Laboratory, managed by UT- Battelle, LLC, for the U.S. Department of Energy under Contract DE-AC05-00OR22725, is sponsored by the Vehicle Technologies Program for the O ffi ce of Energy E ffi ciency and Renewable Energy. The TXM at SSRL was supported by NIH/ NIBIB under Grant Number 5R01EB004321. Portions of this research were carried out at the Stanford Synchrotron Radiation Lightsource, a Directorate of SLAC National Accelerator Laboratory and an O ffi ce of Science User Facility operated for the U.S. Department of Energy O ffi ce of Science by Stanford University. Z.W. acknowledges the support from the Science Fund for Creative Research Groups, NSFC (Grant Number: 11321503), the National Basic Research Program of China (Grant Number: 2012CB825801), and the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant Number: KJCX2-YW-N42).

Uncontrolled Keywords:

Li-ion battery; Li−Mn-rich NMC; X-ray nanotomography; XANES imaging

Subjects:

Chemistry

Divisions:

Department of Chemistry

Depositing User:

Team Library

Date Deposited:

06 Jan 2016 08:21

Last Modified:

18 Oct 2017 06:47