Nickel-Rich Layered Microspheres Cathodes: Lithium/Nickel Disordering and Electrochemical Performance

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• 作者：Chaochao Fu ; Guangshe Li ; Dong Luo ; Qi Li ; Jianming Fan ; Liping Li
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2014
• 出版时间：September 24, 2014
• 年：2014
• 卷：6
• 期：18
• 页码：15822-15831
• 全文大小：756K
• ISSN：1944-8252

文摘

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⁺/Ni²⁺ in local regions of these materials and its impact on electrochemistry performance are not well understood, especially for LiNi_{1鈥?i>x鈥?i>y}Co_xMn_yO₂ (1鈥?i>x鈥?i>y > 0.5) cathodes, which challenge one鈥檚 ability in finding more superior cathode materials for advanced lithium-ion batteries. In this work, Ni鈥揅o鈥揗n-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 LiNi_0.7Co_0.15Mn_0.15O₂ microspheres with different extents of Li⁺/Ni²⁺ disordering. With the determination of the amounts of Li⁺ ions in transition metal layer and Ni²⁺ ions in Li layer using structural refinement, the impact of Li⁺/Ni²⁺ 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 Ni³⁺ content in LiNi_0.7Co_0.15Mn_0.15O₂ as confirmed by X-ray photoelectron spectroscopy and a redox titration. Moreover, the electrochemical performance for as-prepared LiNi_0.7Co_0.15Mn_0.15O₂ microspheres exhibited a trend of deterioration due to the changes of crystal structure from Li⁺/Ni²⁺ mixing. The preparation method and the impacts of Li⁺/Ni²⁺ ions disordering reported herein for the nickel-rich layered LiNi_0.7Co_0.15Mn_0.15O₂ microspheres may provide hints for obtaining a broad class of nickel-rich layered metal oxide microspheres with superior electrochemical performance.

Keywords:

nickel-rich; cathode; LiNi_0.7Co_0.15Mn_0.15O₂ microspheres; lithium/nickel disordering; Li-ion batteries