A gradual capacity increase is one of the most anomalous behaviors in the early stages of battery cycling, which results in an increase in stored energy. This behavior may lead to unstable operation of a battery system or even cause accidents.
A capacity increase is often observed in the early stage of Li-ion battery cycling. This study explores the phenomena involved in the capacity increase from the full cell, electrodes, and materials perspective through a combination of non-destructive diagnostic methods in a full cell and post-mortem analysis in a coin cell.
To further study the capacity increase in 18650 cells at elec-trodes level, a number of advanced techniques have been used in literature to identify and quantify the electrochemical aging behavior in Li-ion batteries , such as incremental capacity and differential voltage (IC-DV) and EIS.
The results show an increase of 1% initial capacity for the battery aged at 100% depth of discharge (DOD) and 45 °C. Furthermore, large DODs or high temperatures accelerate the capacity increase.
The CEs decrease gradually with cycling, which indicates continuous irreversible consumption of the lithium source. However, the capacity continues to increase, which suggests that additional capacities are provided. Fig. 3.
So to establish the required capacitance for a given battery use. In this case, discharge to 0.54V would increase capacitance needed only by about 5%. For an endpoint voltage of 1V you have remaining energy of 1V^2 / 2.7V^2 =~ 14% energy remaining.