am5b11199_si_001.pdf (1.59 MB)
Multi-Functional Surface Engineering for Li-Excess Layered Cathode Material Targeting Excellent Electrochemical and Thermal Safety Properties
journal contribution
posted on 2016-02-04, 19:16 authored by Xiaofei Bian, Qiang Fu, Qiang Pang, Yu Gao, Yingjin Wei, Bo Zou, Fei Du, Gang ChenThe
Li(Li0.18Ni0.15Co0.15Mn0.52)O2 cathode material is modified by a Li4M5O12-like heterostructure and a BiOF surface layer.
The interfacial heterostructure triggers the layered-to-Li4M5O12 transformation of the material which
is different from the layered-to-LiMn2O4 transformation
of the pristine Li(Li0.18Ni0.15Co0.15Mn0.52)O2. This Li4M5O12-like transformation helps the material to keep high
working voltage, long cycle life and excellent rate capability. Mass
spectrometry, in situ X-ray diffraction and transmission electron
microscope show that the Li4M5O12-like phase prohibits oxygen release from the material bulk at elevated
temperatures. In addition, the BiOF coating layer protects the material
from harmful side reactions with the electrolyte. These advantages
significantly improve the electrochemical performance of Li(Li0.18Ni0.15Co0.15Mn0.52)O2. The material shows a discharge capacity of 292 mAh g–1 at 0.2 C with capacity retention of 92% after 100
cycles. Moreover, a high discharge capacity of 78 mAh g–1 could be obtained at 25 C. The exothermic temperature of the fully
charged electrode is elevated from 203 to 261 °C with 50% reduction
of the total thermal release, highlighting excellent thermal safety
of the material.