Surface Surgery of the Nickel-Rich Cathode Material LiNi_0.815Co_0.15Al_0.035O₂: Toward a Complete and Ordered Surface Layered Structure and Better Electrochemical Properties

Abstract

A complete and ordered layered structure on the surface of LiNiCoAlO (NCA) has been achieved via a facile surface-oxidation method with NaSO. The field-emission transmission electron microscopy images clearly show that preoxidation of the hydroxide precursor can eliminate the crystal defects and convert Ni(OH) into layered β-NiOOH, which leads to a highly ordered crystalline NCA, with its (006) planes perpendicular to the surface in the sintering process. X-ray photoelectron spectroscopy and Raman shift results demonstrate that the contents of Ni and Co ions are reduced with preoxidization on the surface of the hydroxide precursor. The level of Li/Ni disordering in the modified NCA determined by the peak intensity ratio I/I in X-ray diffraction patterns decreases. Thanks to the complete and ordered layered structure on the surface of secondary particles, lithium ions can easily intercalate/extract in the discharging-charging process, leading to greatly improved electrochemical properties.

Surface/Interface Structure Degradation of Ni‐Rich Layered Oxide Cathodes toward Lithium‐Ion Batteries: Fundamental Mechanisms and Remedying Strategies

“…Additionally, a preoxidization process before the high temperature calcination, which can largely promote the oxidation of Ni 2+ to Ni 3+ , has also been demonstrated to be an effective way to suppress the Li/Ni disordering . Typically, Wu and co‐workers have successfully synthesized the NCM811 cathode with dramatically decreased Li/Ni cation mixing under air atmosphere with an additional preoxidization process by using the nitrates …”

Insight into the interaction between Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode and BF4−-introducing electrolyte at 4.5 V high voltage

“…5 (a). It has been reported that the smaller value of I (003)/ I (104), the larger the lattice disorder of material structure [45,46] . According to Fig.…”

Preparation, Lithium Storage Performance and Thermal Stability of Nickel‐Rich Layered LiNi0.815Co0.15Al0.035O2/RGO Composites

“…After cycling at 1 C for 200 cycles, there exists one more semicircle in both of the two electrodes (Figure C). According to previous studies,, the semicircle located in high‐to‐medium frequencies corresponds to the resistance of Li + migrating through the surface film of the LNCAO materials (R sf ), while the semicircle at medium‐to‐low frequencies belongs to R ct and the inclined line located in low‐frequencies represents Z w . Note that before and after cycling, all of the resistance in the LNCAO/RGO, including R ct , R sf and Z w , are much lower than those of the LNCAO (Figure A and C).…”

“…synthesized LiNi 0.815 Co 0.15 Al 0.035 O 2 through pre‐oxidation of the commercial Ni 0.815 Co 0.15 Al 0.035 (OH) 2 precursors with the Na 2 S 2 O 8 . Their resulted LNCAO, with complete and ordered layered structures, exhibited improved electrochemical properties . Note that the phenomena of corrosions from the side reactions between LNCAO electrodes and the electrolytes are common and unavoidable in the cathodes .…”