Introduction: British scientists have studied the impact of exposure to the surrounding atmosphere on the nickel-manganese-cobalt cathode of lithium-ion batteries. Although many cathode designs are sensitive to moisture, the team found that nickel-rich cathodes currently gaining market share are particularly fragile and suffer irreversible power losses when exposed to moisture in the air.
Scientists led by the University of Warwick in the United Kingdom investigated the impact of the environment exposed to the atmosphere during production or energy storage on the nickel-rich cathode and found that keeping the material free of moisture is to maximize the use of the battery that will eventually be used The essential. To a large extent, due to the concerns and instability of the cobalt supply chain, battery manufacturers are increasingly turning to cobalt-free or "nickel-rich" designs, usually using 80% nickel, 10% manganese, and 10% Cobalt (NMC 811). Because moisture is a problem for many cathode structures, researchers at the University of Warwick set out to study the mechanism that moisture in the NMC-811 material might trigger, and determine the ideal conditions for manufacturing and storing the cathode before making the battery.
A team of Warwick University exposed the cathode to different temperatures and humidity and then used a series of testing and imaging techniques to analyze its battery performance. The research was described in the paper "The Influence of Environmental Energy Storage Conditions on the Structure and Electrochemical Performance of NMC-811 Cathode of Lithium Battery" published in Electrochimica Acta.
Compared with the control sample, both cathodes are "in the exposed state", while the other cathodes are exposed to moisture and dried, their initial capacity is reduced, and the cycle performance is reduced. The team attributed it to the formation of oxides and carbonates in the material after exposure to the atmosphere, which then irreversibly reduced ions and conductivity.
Melanie Loveridge of the University of Warwick explained: "Although it is well known that the moisture here is problematic, we will determine the best energy storage conditions to reduce unnecessary premature degradation of battery performance. "These measures are essential to increase processing capacity and ultimately maintain performance levels. This is also related to other Ni-rich systems (such as NCA materials). "
Although battery manufacturers are fully aware of the need to protect cathode materials from moisture and the atmosphere, understanding the mechanism that causes problems is very useful for developing moisture-stable materials or determining ideal conditions for the storage and manufacturing of NMC-811 cathodes.
The cathode in this study was exposed for 28 days, and the researchers said this is consistent with the actual storage time that can be seen in the manufacturing plant. However, their next phase of research will focus on the effects of short-term moisture exposure, which will bring more potential for process and material optimization in NMC battery manufacturing.
