Synthesis of Ni-rich NMC cathode material by redox-assisted deposition method for lithium ion batteries

A robust inorganic binder against corrosion and peel-off stress in electrocatalysis

Electrochemical binders used to immobilize electrocatalysts on electrodes are essential in all fields of electrochemistry. However, conventional organic-based binders like Nafion generally suffer from oxidative decomposition at high potentials on anodic electrodes and have high charge transport resistivity. This work proposes the use of acidic redox-assisted deposition to form cobalt manganese oxyhydroxides (CMOH) as a solid-state inorganic binder. CMOH remains stable under high oxidative currents and ensures catalyst adhesion even under significant peel-off stress as shown by experiments involving the alkaline oxygen evolution reaction (OER) using RuO2 as a catalyst immobilized on a rotating disc electrode. While the molecular structure of Nafion decays significantly after 45 minutes under OER conditions at 3.86 V, the CMOH binder is able to support the powder catalysts (RuO2 and NiO x ) showing stability around 1000 mA cm-2 without significant current decay over 24 hours. The robust catalyst adhesion is a result of the formation of chemical bonds between the electrode and the binder and it can be further improved by increasing the applied loading of CMOH. Unlike Nafion, both the OER activity and the diffusion kinetics are not significantly affected by the CMOH binder. It has also been shown that using CMOH as a binder leads to lower charge transfer resistances R ct and higher electrochemical surface areas compared to systems using Nafion. This is partially due to the presence of metal sites in different oxidation states which has been shown to increase intrinsic conductivity, facilitating the charge hopping at the binder/electrocatalyst interface. With this, the present work provides a proof-of-concept for inorganic metal oxides as promising solid-state binders for a wide range of applications in electrochemistry, demonstrating CMOH's outstanding characteristic of strong adhesion to support other highly active but adhesion-weak electrocatalysts.

Layered-Oxide Cathode Materials for Fast-Charging Lithium-Ion Batteries: A Review

Layered oxides are considered prospective state-of-the-art cathode materials for fast-charging lithium-ion batteries (LIBs) owning to their economic effectiveness, high energy density, and environmentally friendly nature. Nonetheless, layered oxides experience thermal runaway, capacity decay, and voltage decay during fast charging. This article summarizes various modifications recently implemented in the fast charging of LIB cathode materials, including component improvement, morphology control, ion doping, surface coating, and composite structure. The development direction of layered-oxide cathodes is summarized based on research progress. Further, possible strategies and future development directions of layered-oxide cathodes to improve fast-charging performance are proposed.

Roll-to-Roll Production of Electrocatalysts Achieving High-Current Alkaline Water Splitting

Scalable production of electrocatalysts capable of performing high-current water splitting is crucial to support green energy utilization. We adopted acidic redox-assisted deposition (ARD) to realize the continuous roll-to-roll fabrication of a strongly adherent cobalt manganese oxyhydroxide (CMOH) film on Ni foam under ambient conditions in water. The as-fabricated products show uniform CMOH coverage and oxygen evolution activities with dimensions as large as 5 m length by 0.25 m width. Also, we converted CMOH into a metallic form (denoted as CM) with the preserved high adhesion to serve as a high-current hydrogen evolution electrocatalyst. Our results reveal that the insufficient adhesion of powder forms electrocatalysts (i.e., Pt and RuO2 as benchmarks), even with the binder, at high-current electrolysis (>1000 mA) can be solved using the fabricated CM||CMOH cell. With an active area of 1 cm × 1 cm assembly in anion exchange membrane (AEM) electrolyzers, we observed the remarkable record of alkaline electrolysis stably at 5000 mA. This result established a new benchmark record on the high-current water splitting research.