Study of Immersion of LiNi_0.5Mn_0.3Co_0.2O₂ Material in Water for Aqueous Processing of Positive Electrode for Li-Ion Batteries

Abstract

The understanding of the phenomena occurring during immersion of LiNi0.5Mn0.3Co0.2O2 (NMC) in water is helpful to devise new strategies toward the implementation of aqueous processing of this high-capacity cathode material. Immersion of NMC powder in water leads to both structural modification of the particles surface as observed by high-resolution scanning transmission electron microscopy and the formation of lithium-based compounds over the surface (LiOH, Li2CO3) in greater amount than after long-time exposure to ambient air, as confirmed by pH titration and 7Li MAS NMR analysis. The surface compounds adversely affect the electrochemical performance and are notably responsible for the alkaline pH of the aqueous slurry, which causes corrosion of the aluminum collector during coating of the electrode. The corrosion is avoided by adding phosphoric acid to the slurry as it lowers the pH, and it also enhances the cycling stability of the water-based electrodes due to the phosphate compounds formed at the particles surface, as evidenced by X-ray photoelectron spectroscopy analysis.

Clean the Ni-Rich Cathode Material Surface With Boric Acid to Improve Its Storage Performance

“…However, although increased nickel content in Ni-rich cathode materials enables them to deliver higher capacity, more residual lithium compounds (RLCs) will be formed on their surface. The RLC mainly contains Li 2 O, Li 2 O 2 , LiOH, LiHCO 3 , and Li 2 CO 3 (Liu et al, 2004;Kim et al, 2006;Bichon et al, 2019;Zhang et al, 2019), which origins from the vestigial of lithium salts and spontaneous reduction reaction of Ni 3+ during the synthesis and storage process (Junhyeok et al, 2018). In detail, excess 5 mol% lithium salts are usually applied to compensate the evaporation loss during high-temperature calcination process (Liang et al, 2017).…”

“…This undesired RLC has many adverse effects on the Nirich materials. First, RLC would absorb the trace water in the air and increase the powder alkalinity, which will further gel the slurry during electrode fabrication process, corrode the current collector, and worsen the consistency of electrode and the corresponding batteries (He et al, 2018;Junhyeok et al, 2018;Bichon et al, 2019). Second, this insulating RLC would also react with the electrolyte and produce gas such as CO 2 , thus deteriorating the electrochemical performances and causing safety problem (Hatsukade et al, 2018).…”

First-Principles and Thermodynamics Comparison of Compositionally-Tuned Delafossites: Cation Release from the (001) Surface of Complex Metal Oxides

“…The set of 333-ABC presented here yields insights into further developing technologies based on the CMO surface and its interface with aqueous media or the gas phase. Understanding the pH dependent behavior of CMO compositions is key to devising new strategies for cost-effective aqueous material processing, 53 increasing battery longevity, 54 and how…”

Operation, Manufacturing, and Supply Chain of Lithium-ion Batteries for Electric Vehicles

“…[111][112][113] However, the more cost-effective route may be pH modification, which has been achieved most commonly by adding acids. [114][115][116][117][118][119][120] Some of these acids have been shown to provide the additional benefit of protecting the surface of active materials from further Li depletion.…”