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Gradient-morph LiCoO2 single crystals with stabilized energy density above 3400 W h L−1

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Abstract

The cycling stability of LiCoO2 under high voltages (>4.5 V) was plagued by hybrid anion- and cation-redox (HACR) induced oxygen escape and uncontrolled phase collapse. With DEMS and in situ XANES mapping at the NSLS-II, we demonstrate that oxygen escape triggers irreversible transformations into “bad” surface phases that rapidly propagate inward. Enabling HACR but stopping global oxygen migration is key to a stable high-energy cathode. Therefore, we developed ∼10 μm single crystals with LiCoO2 in the bulk smoothly transitioning to Co-free LiMn0.75Ni0.25O2 at the surface. By means of initial electrochemical formation, a semi-coherent LiMn1.5Ni0.5O4 spinel-like shell was established in operando with little oxygen loss to integrally wrap the LiCoO2 bulk. Then we obtained gradient-morph LiCoO2 single crystals to prevent the percolating migration of oxygen out of the particle and achieved enhanced HACR reversibility at high voltages. The gradient-morph HACR cathode undergoes substantially stabilized cycling when charged to above 4.6 V, and hence a stable cyclic volumetric energy density of >3400 W h L−1 has been achieved in a pouch full-cell coupled with a commercial graphite anode and lean electrolyte (2 g A h−1), exhibiting up to 2906 W h L−1 even after 300 cycles.

Graphical abstract: Gradient-morph LiCoO2 single crystals with stabilized energy density above 3400 W h L−1

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Supplementary files

Article information


Submitted
22 Jan 2020
Accepted
14 Apr 2020
First published
20 May 2020

This article is Open Access

Energy Environ. Sci., 2020, Advance Article
Article type
Paper

Gradient-morph LiCoO2 single crystals with stabilized energy density above 3400 W h L−1

Z. Zhu, D. Yu, Z. Shi, R. Gao, X. Xiao, I. Waluyo, M. Ge, Y. Dong, W. Xue, G. Xu, W. Lee, A. Hunt and J. Li, Energy Environ. Sci., 2020, Advance Article , DOI: 10.1039/D0EE00231C

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