A high capacity retention, along with a long battery life, are two aspects paramount towards the economic viability of large-scale Lithium-Ion battery (LIB) applications. As such, it is important to understand the mechanisms underlying capacity decay, as to mitigate them, if not outright reverse them. To that end, there have been many studies addressing this issue. However, most of these studies have relied on varying only a limited amount of parameters, thus limiting the scope, and depth of their conclusions: if two variables have a covariant relationship, yet the experiment only accounts for one, the presence of that relationship will be obscured.

Herein, the current research explores the long-term fading in lithium-batteries, and how it is affected by a host of different factors, ranging from cycling temperature, and current rate, to initial formation, and restive period at the top of charge. These studies go on to reveal that there exists a very strong relationship between current rate, and temperature, as it pertains to fading, with higher temperatures showing surprisingly high capacity retention over the long term (Figure 1). Furthermore, we are further able to demonstrate that under certain conditions, capacity losses are recoverably, which thus alludes to the possibility of being able to prolong, if not recycle, LIBs currently in use.

Lastly, this work also explores one of the big divides that still exists within the battery community: the testing of long-term cycling in Li-metal half cells, as opposed to full cells. Our experimental results show that the nature of fading mechanisms in full-cells versus half-cells are not analogous to one another. Certain mechanisms that dominate in one medium, have a greatly diminished presence in the other. As such, this work concludes by stressing the question: what is the proper way, if any, to look at long term fading mechanism in LIBs?