HI John, I would like to see where you got that idea from. I like reading original material. "Other ion paths" is not clear to me.
My understanding is different. Batteries store chemical potential energy. There is no electric field as far as I know when you create a stable "new chemical" - in this case a lithiated negative electrode. The electrolyte isn't an insulator though you can measure the dielectric strength and argue about when that is or isn't an insulator. The electrolyte is a place for lithium ions to reside between the electrodes by way ol the lithium salt dissolved in it), but the separator (called such because that is its purpose to put some distance between the electrodes and reduces the chance of shorts) provides a volume for the electrolyte to fill. The ions in the electrolyte don't really flow. It is more like the desk toy of balls on strings and you pull an end and one away and let it go, it strikes then the far ball pops out. Even though the gap is very small and the ions can migrate, Jeff Dahn told me it takes a minute or so for an ion to actually traverse the very thin electrolyte from one electrode to the other. When a cell has lost its capacity it is because the ions in the electrolyte have been depleted by unhealthy chemical reactions at the positive electrode. There are fewer ionic "balls" in the electrolyte to knock ions from one electrode to the other. When the ions are intercalated in the negative electrode it is a new stable chemical that is created. It is even more reactive with the electrolyte and would tear it up if not for the SEI that forms. The new chemical formed in the positive electrode - the de-lithiated lithium metal oxide (or phosphate) - is also much more reactive than the discharged state chemical. No SEI forms here, and this is where the trouble starts for li ion cells when the temperature and SOC are to high because of the highly reactive nature of the chemical of the discharged positive electrode. When you let an electron pass from the negative electrode to the positive and ion de-intercalates and bangs an ion back into the Positive electrode. Cells, when designed well, don't offer a ready path for any electrons that aren't controlled by external circuitry. This how cells for medical implants can last for 10 or more years. If some poorly designed cells do offer a way to discharge spontaneously, that is a bad thing. It is incorrect to indict all lithium cells with this concept. You can do all you like to a lead acid cell and it will lose its charge internally. It doesn't have an intercalation function. The chemicals formed during charging naturally return to the discharged state over time and with temperature. On Tue, Jun 23, 2015 at 7:35 PM, John Lindsay via EV <ev@lists.evdl.org> wrote: > There are other ion paths from impurities in the electrodes and > electrolyte that allow charge to flow in the other direction thus closing > the circuit. > > John Lindsay > johnslind...@mac.com > +61403577711 > > -- To invent, you need a good imagination and a pile of junk. Thomas A. Edison <http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html> A public-opinion poll is no substitute for thought. *Warren Buffet* Michael E. Ross (919) 585-6737 Land (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone (919) 631-1451 Cell michael.e.r...@gmail.com <michael.e.r...@gmail.com> -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20150623/56e56c51/attachment.htm> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
