Nickel-rich layered oxides, as the
most promising commercial cathode
material for high-energy density lithium-ion batteries, experience
significant surface structural instabilities that lead to severe capacity
deterioration and poor thermal stability. To address these issues,
radially aligned grains and surface Li
x
Ni
y
W
z
O-like
heterostructures are designed and obtained with a simple tungsten
modification strategy in the LiNi0.91Co0.045Mn0.045O2 cathode. The formation of radially
aligned grains, manipulated by the WO3 modifier during
synthesis, provides a fast Li+ diffusion channel during
the charge/discharge process. Moreover, the tungsten tends to enter
into the lattice of the primary particle surface, and the armor-type
tungsten-rich heterostructure protects the bulk material from microcracks,
structural transformations, and surface side reactions. First-principles
calculations indicate that oxygen is more stable in the surface tungsten-rich
heterostructure than elsewhere, thus triggering an improved surface
structural stability. Consequently, the 2 wt % WO3-modified
LiNi0.91Co0.045Mn0.045O2 (NCM@2W) material shows outstanding prolonged cycling performance
(capacity retention of 80.85% after 500 cycles) and excellent rate
performance (5 C, 188.4 mA h g–1). In addition,
its layered-to-rock salt phase transition temperature is increased
by 80 °C compared with that of the pristine cathode. This work
provides a novel surface modification approach and an in-depth understanding
of the overall performance enhancement of nickel-rich layered cathodes.
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