I know both from online websites and from experience that discharging a li-ion battery below 50% greatly decreases its life and capacity.

But why is it so?


There are two main effects that cause damage to a Li-ion battery due to "deep cycling":

  1. During the charge/discharge cycle, lithium ions are intercalated within the electrodes. This causes physical stress to the electrode material and spalling of their coatings. Deeper discharge causes increased stress. This effect is made worse with the temperature range from heavy current use as in a laptop.

  2. Lithium metal may accumulate on the anode, taking it out of play. This effect may be due more to over-charging than to deep-discharge, though.

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  • $\begingroup$ But deep cycling is not below 50% but more below somewhat around 7-10% afaik. $\endgroup$ – pH13 - Yet another Philipp Oct 9 '15 at 15:36
  • $\begingroup$ Deep cycling means a large change in charge, not just a specific charge state. $\endgroup$ – DrMoishe Pippik Oct 9 '15 at 15:46
  • $\begingroup$ Ok, then go ahead. $\endgroup$ – pH13 - Yet another Philipp Oct 9 '15 at 16:09

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