One of the reasons for Cell capacity recovery during rest.
Regular rest periods or characterizations during accelerated cyclic ageing tests lead to an increase in the measured cell capacity as well as to a longer lifetime of the cells. A capacity increase is measured even if the cell is left at 100% SoC during the rest period. This excludes the anode overhang as the source of the capacity increase [1].
I don't see how exactly resting at 100% SoC excludes anode overhang effects as the possible reason for capacity recovery.
As far as I understand, when a cell is cycled at a fast pace, the overhanging areas of the anode achieve the equilibrium SoC which is approximately the average SoC of the non-overhanging parts of the anode during cycling. Thus, when a cell is rested at 100% SoC, some of the Lithium from non-overhanging parts can move to the overhanging parts.
If we measure the capacity of the cell as the amount of charge that we can extract from it immediately after the rest period, then resting at 100% should decrease the capacity (or at least not increase it), indeed. However, if there is still some Lithium in the cathode (or excess Lithium in the electrolyte) while the cell was rested at 100% SoC, and we measure the cell capacity over a full charge-discharge cycle (e. g., following the Precise cell capacity measurement protocol), then it might appear that the cell capacity has increased. This can happen because on top of the full "baseline" discharge capacity, the anode overhang can supply additional Lithium to be released into the electrolyte while the cell is discharging.
And, in fact, the authors write that they were measuring capacity during the second discharge phase after a rest period. To me, this seems to be compatible with the theory that anode overhang effects can increase the measured cell capacity.
[2] confirms this effect as well:
On this diagram, SNN means the SoC level at which a cell was stored before cycling.
[3] also articulates the same conclusion.
Related:
See also:
[2] Cycling capacity recovery effect: A coulombic efficiency and post-mortem study
[3] ‣