Role of fluorine surface modification in improving electrochemical cyclability of concentration gradient Li[Ni_0.73Co_0.12Mn_0.15]O₂ cathode material for Li-ion batteries

Abstract

The fluorine-modified Li[Ni0.73Co0.12Mn0.15]O2−xFx materials exhibit superior cycling stability, which is attributed to the synergistic protection of the surface NiO-like phase and fluoride layer.

Review on Synthesis, Characterization, and Electrochemical Properties of Fluorinated Nickel‐Cobalt‐Manganese Cathode Active Materials for Lithium‐Ion Batteries

“…The strong peak around 533 eV is attributed to inorganic Li 2 CO 3 formed by the reaction of residual LiOH with atmospheric CO 2 . Furthermore, the measurements indicate that Li 2 CO 3 reacted with [NH 4 ]FHF during the F‐modification procedure to LiF, which is consistent with the FT‐IR results (see above) . Li 1.23 Ni 0.13 Co 0.14 Mn 0.56 O 2‐z F z (z=0 and 0.15; co‐precipitation method; F‐source: [NH 4 ]FHF).…”

“…Therefore, the surface of the pristine CAM included Li 2 CO 3 . It is noteworthy that the intensity of the absorption peaks gradually weakens with increasing fluoride amount, which suggests that the surface Li 2 CO 3 residues are decreased by the F‐modification . However, in HE‐NCM treated with F 2 , all obtained IR spectra appeared to be identical and showed the typical characteristic bands for HE‐NCM material …”

“…1). Fluorination of NCM CAMs was performed by the reaction of finely ground pristine NCM material (such as Li 1.23 Ni 0.13 Co 0.14 Mn 0.56 O 2 and LiNi 0.73 Co 0.12 Mn 0.15 O 2 ) with [NH 4 ]FHF during calcination at 450 °C to 500 °C for 5 h in air . Equations (2) to (3) indicate the processes possibly inducing the reaction of [NH 4 ]FHF with the pristine material. …”

Origin of Performance Differences of Nickel‐Rich LiNi0.9Mn0.1O2 Cathode Materials Synthesized in Oxygen and Air

“…The occupancy of Ni at the Li site for A‐LNMO is derived to be 7.2%, twice that for O‐LNMO, indicating the more severe cation intermixing for A‐LNMO . Both I (003) / I (104) and c / a for O‐LNMO are larger than those for A‐LNMO, implying its better ordered structure, which facilitate the electrochemical performance . The smaller lattice parameters of O‐LNMO reasonably lead to its shorter Ni—O and Li—O bonds in which the Ni—O bond decreases by 0.006 Å but the Li—O bond decreases only by 0.0011 Å.…”

“…Their large differences in impedance are clearly evidenced, which are associated with different surface states, that is, different thickness of Li 2 CO 3 layers with poor electrical conductivity. The lower R ct and R SEI of O‐LNMO lead to the faster Li + intercalation kinetics and thus the better rate capability, which is also evidenced by its higher Li + transport coefficient.…”