Design, preparation and properties of core-shelled Li{[NiyCo1-2yMny](1-x)}core{[Ni1/2Mn1/2]x}shellO2 (0≤x≤0.3, 6y+3x-6xy=2) as high-performance cathode for Li-ion battery

• LiNi1/3Co1/3Mn1/3O2 is designed into new core-shelled structure.
• Core-shelled layered oxides present better cycleability.
• The significantly improved safety property is observed for core-shelled samples.

LiNi1/3Co1/3Mn1/3O2 was redesigned into new core-shelled Li{[NiyCo1-2yMny](1-x)}core{[Ni1/2Mn1/2]x}shellO2 (0 ≤ x ≤ 0.3, 6y + 3x-6xy = 2) to improve its performances. Those core-shelled materials were successfully synthesized at 800 °C from core-shelled {[NiyCo1-2yMny](1-x)}core{[Ni1/2Mn1/2]x}shell(OH)2 precursors obtained via a co-precipitation route. Scanning Electron Microscope (SEM) shows that a morphology with good spherical secondary particles developed from needle-like primary particles was formed in the precursors and maintained well in the lithiated compounds even after the calcination at 800 °C. Energy Disperse X-ray Spectrum (EDS) on the surface of precursors particles, in combination with evidence of size increase from core to shell during co-precipitation process, supports the formation of the core-shell structure as designed in the precursors. This is certified by subsequent EDS experiments on the cross-section of single particle of the lithiated compounds, showing that the lithiated compounds approximately had a targeted core-shell structure of Li{[NiyCo1-2yMny](1-x)}core{[Ni1/2Mn1/2]x}shellO2. Nevertheless, it is hard to detect differences in XRD for those lithiated compounds. Electrochemical tests and Differential Scanning Calorimetry (DSC) experiments demonstrate the gradually improved cyclability at a severe charge-discharge condition (55 °C and charging to 4.5 V) and thermal stability of materials with increasing x value (thickness of shell).

Figure optionsDownload as PowerPoint slide