The life of lithium battery is mainly reflected in the charge-discharge cycle, which is an absolute concept. Last time, I used 30% electricity and was fully charged. Next time, I used 70% electricity and was fully charged. This is just a charging cycle. Therefore, we still use the slogan of the inventor of lithium battery "charging immediately means charging immediately".

Charging for a long time and completely discharging will lead to overcharge and overdischarge, which will cause permanent damage to the anode and cathode of lithium-ion batteries. From the molecular level, excessive discharge will lead to the release of too many lithium ions from negative carbon, which will lead to the collapse of its lamellar structure. Overcharging will force too many lithium ions into the negative carbon structure, some of which will never be released. This is why lithium-ion batteries are usually equipped with charge and discharge control circuits.

Under normal circumstances, the battery should be charged with reserve according to the principle that the remaining battery power is used up (but it is definitely not used for shutdown charging). If the battery is not expected to be used for a whole day the next day, it should be charged in time. However, when charging is needed to cope with important events that are expected to lead to busy communication in the near future, even if the battery still has a lot of remaining power, it is only charged in advance, because it does not really lose a charging cycle life. The principle of recharging after the battery is used up is not to let you go to extremes. Like charging for a long time, it is generally said that "try to use up the battery of the mobile phone, and it is best to turn it off automatically". In fact, this practice is only on nickel batteries, in order to avoid the "memory effect." Unfortunately, today it also spreads in lithium batteries.