Some links Micah provided on Self-discharge:
https://www.mpdigest.com/2021/08/23/a-deeper-look-at-lithium-ion-cell-self-discharge-measurement-method/
How Keysight measures self-discharge:
https://www.keysight.com/ca/en/assets/7018-06913/data-sheets/5992-4211.pdf
What is Lithium-Ion cell self-discharge?
How can self-discharge be measured in Li-Ion cells? Part 1
How can self-discharge be measured in Li-Ion cells? Part 2