The explanation for self charge, but require knowledge of quantum physics:
https://cdn-pubs.acs.org/doi/suppl/1...322_si_001.pdf
"The nature of self-charge.
1. There are two self-charge processes; one is without plating and one is with an anode plating. The first and more common happens in almost all kinds of battery cells (if anode and cathode show an open circuit voltage different from zero) especially in “charged cells” that are not charged prior to discharge (e.g. primary cells). This phenomenon of self-charge does not involve plating of an anode, it happens due to the necessity to align each electrode’s Fermi level with the electrolyte’s Fermi level in contact with the electrodes at the electrode/electrolyte interface as demonstrated in ref. [S1]. The anode is at a higher Fermi level than that of the electrolyte and cathode. To align the higher Fermi level of the anode with the lower Fermi level of the electrolyte, an Electrical Double Layer Capacitor (EDLC) is formed at the interface in a way that the potential (energy per unit charge) increases in the direction of the electrolyte (Fig. S9). Therefore, the electric field has to pointing the direction of the anode and hence the free electrons that accumulate at the surface of the anode at the anode/electrolyte interface and the mobile cations in the electrolyte form an EDLC. On the cathode side, the electric field has to point towards the electrolyte and electron deficiencies holes on the cathode side form an EDLC with cation deficiencies in the electrolyte.
2. The second self-charge phenomenon is characteristic of the present electrolyte containing both ions and dipoles; it involves a plating of an anode from the working cation of the electrolyte; as shown in the paper, we argue that this self-charge is the result of equalization of the Fermi levels across the negative-electrode/electrolyte interface and a time lag between the arrival at the interface of the fast-moving electrolyte cation and the slower-moving electrolyte electric dipoles. Equalization of the Fermi levels by the interface EDLC (Fig. S9) is retained on arrival of the electric-dipole charge by a plating of an electrolyte cation onto the negative electrode, i.e. a self-charge, that creates a negative charge in the electrolyte.
3. Self-charge due to alignment of the dipoles.
According to Gauss’s law, the electric field outside a parallel plate capacitor (EDLCs) is zero. Therefore, the fields E’ and E’’ of Fig. S10 must sum to zero in the bulk electrolyte when no dipoles are aligned. The alignment of the dipoles leading to a uniform array is equivalent to a surface charge. The electric field E’’’ resulting from the alignment of the electric dipoles inside the electrolyte must be compensated by the surface charge in the electrolyte/electrode EDLCs. The surface charge increment results in a higher E’’ that then compensates E’’’ and E’ in the electrolyte. "
If she managed to well explain this to a layman language she will get the Nobel Prize of pedagogy.