Noticeably fewer decomposition products were detected in NMC/graphite cells compared to NMC/Li xFePO 4 cells, which is ascribed to the consumption of water (from the reaction of 1O 2 and EC) at the graphite electrode, preventing secondary decomposition reactions. The water that is produced initiates secondary reactions, leading to the formation of the various products identified by NMR spectroscopy. The formation of water via this mechanism was confirmed by reacting 17O-labelled 1O 2 with EC and characterising the reaction products via 1H and 17O NMR spectroscopy.

At low potentials (80% SOC), 1O 2 released from the transition metal oxide chemically oxidises the electrolyte solvent (EC) to form CO 2, CO and H 2O. Based on the detected soluble and gaseous products, two distinct routes with different onset potentials are proposed for the decomposition of the electrolyte solution at NMC electrodes. A partially delithiated LFP (Li xFePO 4) counter electrode was used to selectively identify the products formed through processes at the positive electrodes. In this work, a combination of operando gas measurements and solution NMR was used to study decomposition reactions of the electrolyte solution at NMC (LiNi xMn 圜o 1− x− yO 2) and LCO (LiCoO 2) electrodes. However, the exact mechanism(s) for electrolyte decomposition at the positive electrode, and particularly the soluble decomposition products that form and initiate further reactions at the negative electrode, are still largely unknown. Finally, it is calculated and proved that the Al–O bonding stability under the TM–O octahedral coordination system is much greater than the Mn–O bonding stability.Preventing the decomposition reactions of electrolyte solutions is essential for extending the lifetime of lithium-ion batteries. The existence of oxygen vacancies provides a channel for the migration and dissolution of transition metal atoms. Besides, first principles calculations were used to calculate the difficulty of generating oxygen vacancies in LiNi 0.85Co 0.1Al 0.05O 2 and LiNi 0.8Co 0.1Mn 0.1O 2 during cycling, and the result showed that the formation energy of vacancy defects of O adjacent to the dopant atoms in the Al doped structure is higher than that of the Mn doped structure. The Mn dissolution will lead to more serious Li/Ni mixing and Ni dissolution, which would finally cause the worse structural stability of LiNi 0.8Co 0.1Mn 0.1O 2. Characterization of the internal structure and the chemical composition of materials after cycles indicated serious Mn dissolution in LiNi 0.8Co 0.1Mn 0.1O 2 during the long cycles. It is found that LiNi 0.85Co 0.1Al 0.05O 2 delivers a better cycling stability than LiNi 0.8Co 0.1Mn 0.1O 2, even with a higher nickel content. Herein, LiNi 0.85Co 0.1Al 0.05O 2 and LiNi 0.8Co 0.1Mn 0.1O 2 were synthesized by the co-precipitation method. However, there is still a lack of systematic research on the pros and cons of these two nickel-rich materials in industry. As two typical layered nickel-rich ternary cathode materials, NCA and NCM are expected to be commercialized in lithium-ion power batteries.

Nmc cathode wiki