title: Nickel-rich layered microspheres cathodes: lithium/nickel disordering and electrochemical performance.
abstract: Nickel-rich layered metal oxide materials are prospective cathode materials for lithium ion batteries due to the relatively higher capacity and lower cost than LiCoO2. Nevertheless, the disordered arrangement of Li(+)/Ni(2+) in local regions of these materials and its impact on electrochemistry performance are not well understood, especially for LiNi(1-x-y)Co(x)Mn(y)O2 (1-x-y > 0.5) cathodes, which challenge one's ability in finding more superior cathode materials for advanced lithium-ion batteries. In this work, Ni-Co-Mn-based spherical precursors were first obtained by a solvothermal method through handily utilizing the redox reaction of nitrate and ethanol. Subsequent sintering of the precursors with given amount of lithium source (Li-excess of 5, 10, and 15 mol %) yields LiNi0.7Co0.15Mn0.15O2 microspheres with different extents of Li(+)/Ni(2+) disordering. With the determination of the amounts of Li(+) ions in transition metal layer and Ni(2+) ions in Li layer using structural refinement, the impact of Li(+)/Ni(2+) ions disordering on the crystal structure, valence state of nickel ions, and electrochemical performance were investigated in detailed. It is clearly demonstrated that with increasing the amount of lithium source, lattice parameters (a and c) and interslab space thickness of unit cell decrease, and more Li(+) ions incorporated into the 3a site of transition metal layer which leads to an increase of Ni(3+) content in LiNi0.7Co0.15Mn0.15O2 as confirmed by X-ray photoelectron spectroscopy and a redox titration. Moreover, the electrochemical performance for as-prepared LiNi0.7Co0.15Mn0.15O2 microspheres exhibited a trend of deterioration due to the changes of crystal structure from Li(+)/Ni(2+) mixing. The preparation method and the impacts of Li(+)/Ni(2+) ions disordering reported herein for the nickel-rich layered LiNi0.7Co0.15Mn0.15O2 microspheres may provide hints for obtaining a broad class of nickel-rich layered metal oxide microspheres with superior electrochemical performance.
authors.affiliation: Key Lab of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, and ‡State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, University of Chinese Academy of Sciences , Fuzhou 350002, P. R. China.
authors.forename: Chaochao
authors.initials: C
authors.lastname: Fu
authors.forename: Guangshe
authors.initials: G
authors.lastname: Li
authors.forename: Dong
authors.initials: D
authors.lastname: Luo
authors.forename: Qi
authors.initials: Q
authors.lastname: Li
authors.forename: Jianming
authors.initials: J
authors.lastname: Fan
authors.forename: Liping
authors.initials: L
authors.lastname: Li
keywords: Li-ion batteries; LiNi0.7Co0.15Mn0.15O2 microspheres; cathode; lithium/nickel disordering; nickel-rich