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.

Multishelled Ni‐Rich Li(NixCoyMnz)O2 Hollow Fibers with Low Cation Mixing as High‐Performance Cathode Materials for Li‐Ion Batteries

“…After 300 electrochemical cycles, the capacity retention was 84.36% for x = 0.8. This performance level is far superior to most Ni‐rich electrodes reported (Figure 4e) 1, 2, 25. Even when the Li/Li(Ni x Co y Mn z )O 2 cells were tested at a high cut‐off potential of 4.6 V versus Li/Li + for 100 cycles (Figure S9, Supporting Information), the capacity retention for the electrode with x = 0.5 was still 91.40%, much higher than the best previously reported value of 85% 12.…”

An Ostwald ripening route towards Ni-rich layered cathode material with cobalt-rich surface for lithium ion battery

“…The ratios of c/a and I (003) /I (104) increase with the increase of Co content, indicating lower cation disorder for the Ni-rich layered cathode with Co-rich surface. A more superior layered structure and lower degree of the cation mixing for Ni-rich cathodes with Co-rich surface may help to improve the electrochemical performance [67,68].…”

“…After 200 cycles the as-prepared NCM, NCM-Co-1 and NCM-Co-2 deliver discharge capacities of 137.5, 159.2, and 151.8 mA h g −1 , corresponding to the capacity retention of 76.4%, 90.5%, and 87.7%, respectively. The rapid capacity fade of NCM can be ascribed to the successive phase transitions from H2 to H3 and the severe side reactions of the Ni-rich cathode surface with the electrolyte [68]. The Co-rich surface of Ni-rich layer cathodes can play an effective role in inhibiting the disorder of cations, enhancing the structural stability, and diminishing side reactions between the electrolyte and extremely unstable Ni 4+ in highly delithiated Ni-rich cathode material.…”

Properties of LiNi0.8Co0.1Mn0.1O2 as a high energy cathode material for lithium-ion batteries

“…The unit cell parameters are calculated and summarized in Table 2. The 'a' cell parameter is the measure of the intralayer metal-metal distance and the ' c' parameter is the sum of the MO 6 (M=transition metal) octahedra layer (slab) thickness (slab thickness S) and LiO 6 octahedra layer thickness (interslab thickness I) in the lamellar structure of LiMO 2 [35]. Therefore, the increase in the parameter reflects an increase in the effective ionic radius.…”