A Novel Cathode Material with a Concentration-Gradient for High-Energy and Safe Lithium-Ion Batteries

다국어 초록 (Multilingual Abstract)

<P>A high-energy functional cathode material with an average composition of Li[Ni<SUB>0.72</SUB>Co<SUB>0.18</SUB>Mn<SUB>0.10</SUB>]O<SUB>2</SUB>, mainly comprising a core material Li[Ni<SUB>0.8</SUB>Co<SUB>0.2</SUB>]O<SUB>2</SUB> encapsulated completely within a stable manganese-rich concentration-gradient shell is successfully synthesized by a co-precipitation process. The Li[Ni<SUB>0.72</SUB>Co<SUB>0.18</SUB>Mn<SUB>0.10</SUB>]O<SUB>2</SUB> with a concentration-gradient shell has a shell thickness of about 1 µm and an outer shell composition rich in manganese, Li[Ni<SUB>0.55</SUB>Co<SUB>0.15</SUB>Mn<SUB>0.30</SUB>]O<SUB>2</SUB>. The core material can deliver a very high capacity of over 200 mA h g<SUP>−1</SUP>, while the manganese-rich concentration-gradient shell improves the cycling and thermal stability of the material. These improvements are caused by a gradual and continuous increase of the stable tetravalent Mn in the concentration-gradient shell layer. The electrochemical and thermal properties of this cathode material are found to be far superior to those of the core Li[Ni<SUB>0.8</SUB>Co<SUB>0.2</SUB>]O<SUB>2</SUB> material alone. Electron microscopy also reveals that the original crystal structure of this material remains intact after cycling.</P>
<B>Graphic Abstract</B>
<P>A novel high-energy functional cathode material with an average composition of Li[Ni<SUB>0.72</SUB>Co<SUB>0.18</SUB>Mn<SUB>0.10</SUB>] O<SUB>2</SUB>, mainly comprising a core material Li[Ni<SUB>0.8</SUB>Co<SUB>0.2</SUB>] O<SUB>2</SUB> encapsulated completely within a stable manganese-rich concentration-gradient shell was successfully synthesized. This material shows very a high reversible capacity of 193 mA h g<SUP>−1</SUP> as well as excellent cycling and thermal stability.
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