Issue 14, 2019

Co-regulating the surface and bulk structure of Li-rich layered oxides by a phosphor doping strategy for high-energy Li-ion batteries

Abstract

Li-rich layered materials, despite their high specific capacity up to 250 mA h g−1, suffer from structural transformation either in the initial activation or after cycling, causing continuous voltage decay and capacity fading. Anion doping has been widely considered as a way to stabilize the intrinsic structure and improve the electrochemical performance of Li-rich materials, though with the pain of process complexity and limitation. Here, we report a simple co-precipitation method with a dual sedimentating agent to realize phosphor doping in both the surface and bulk. X-ray diffraction Rietveld refinement results indicate that the doped sample presents a larger lattice spacing than the normal sample and a Li3PO4 protective layer in situ forms on the surface. Synchrotron scanning transmission X-ray microscopy (STXM) reveals commendable homogeneity in the phase distribution between the surface and bulk in the doped sample. X-ray absorption near edge structure (XANES) shows a more homogeneous local chemical environment of the doped sample by investigating the Mn, Ni, and Co L-edges and O K-edge spectra. The doped sample displays a high discharge capacity of 295 mA h g−1 with an initial coulombic efficiency of 90.5% at 0.1C, showing a high rate performance of 247 mA h g−1 at 1C and a superior capacity retention of 73% after 500 cycles. Moreover, this doping strategy also inhibits the critical voltage decay of Li-rich materials during cycling. The prolonged structural evolution analysis demonstrates that phosphor doping can play a stabilizing role in Li-rich materials to restrain the transformation from layer to spinel.

Graphical abstract: Co-regulating the surface and bulk structure of Li-rich layered oxides by a phosphor doping strategy for high-energy Li-ion batteries

Supplementary files

Article information

Article type
Paper
Submitted
21 Jan 2019
Accepted
04 Mar 2019
First published
05 Mar 2019

J. Mater. Chem. A, 2019,7, 8302-8314

Co-regulating the surface and bulk structure of Li-rich layered oxides by a phosphor doping strategy for high-energy Li-ion batteries

M. Wang, F. Yu, G. Sun, J. Wang, J. Zhou, D. Gu and Z. Wang, J. Mater. Chem. A, 2019, 7, 8302 DOI: 10.1039/C9TA00783K

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