The battery of a mobile phone can only be charged when it automatically shuts down; otherwise, it will "hold a grudge" and become shorter and shorter as time goes by! Charging the battery all night will cause it to "wear out", and it will be scrapped after two years! "Fast charging is very harmful to the battery. Only by always using slow charging can the lifespan be prolonged..." Do you also firmly believe these "words of experience" about lithium batteries?

In fact, many of the widely circulated "battery maintenance secrets" are essentially the cognitive inertia of the nickel-cadmium battery era or misunderstood technical details. Especially the concept of "memory effect" has long been proven by scientific experiments to have nothing to do with lithium batteries. This article will disassemble several core misunderstandings about lithium batteries and clear up your doubts with scientific principles.

Five Common Misconceptions about Lithium Batteries: Tackle Them One by One!

Based on the misunderstanding of the "memory effect", many misconceptions about lithium batteries have emerged. The following are the five most typical misunderstandings, which are debunked one by one in combination with scientific and experimental data:

Misconception 1: "Lithium batteries must be completely discharged before recharging; otherwise, they will become ‘passivated‘."

The truth is that lithium batteries are strictly prohibited from being fully discharged. Deep discharge (with a capacity of less than 10%) will instead accelerate damage.

In the era of nickel-cadmium batteries, "regular complete discharge" was to prevent the accumulation of crystalline layers. However, the negative electrode of lithium batteries is graphite, and its layered structure allows lithium ions to freely intercalate and deintercalate, eliminating the problem of "passivation". On the contrary, if a lithium battery is discharged for a long time until it is completely drained (automatically shuts down or even lower), the lithium ions on the surface of the negative electrode will be unable to intercalate in time and form "dead lithium" (metallic lithium particles). These "dead lithium" cannot participate in subsequent charging and discharging reactions, which will lead to a permanent loss of battery capacity.

The correct approach: The optimal charging range for lithium batteries is 20% to 80% (for daily use). Occasionally charging to 100% or reaching 30% does not have a significant impact, but it is advisable to avoid long-term charging below 20% or above 90%.

Misconception 2: "Charging the battery all night will ‘wear out‘ it and shorten its lifespan."

The truth is that the BMS (Battery Management System) of modern lithium batteries has solved the problem of "overcharging", and the impact of charging overnight has been overly magnified.

Early nickel-cadmium batteries, lacking overcharge protection, could cause the electrolyte to boil, the battery to expand and even explode when charged for a long time. However, the BMS of lithium batteries will cut off the main charging circuit when the battery reaches 100%, retaining only a small current (" trickle charging ") to maintain voltage stability. At this point, the battery is in a "fully charged standby" state and will not continue to be charged in large quantities.

Experimental data show that in an environment of 25℃, when a lithium battery is fully charged and stored for 24 hours, the capacity attenuation is only about 0.01%. Even after continuous storage for 7 days, the attenuation is controlled within 0.1% (far lower than the influence of high temperature or deep discharge). What really damages the battery is long-term full charge storage and high-temperature environments (such as exposure to the sun inside the car in summer), at which point the decomposition of the electrolyte accelerates, leading to a significant decrease in capacity.

The correct approach: There is no need to worry about charging throughout the night, but try to avoid long-term exposure to high-temperature environments (such as above 35℃) when fully charged.

Misconception 3: "Fast charging is very harmful to batteries. Only by always using slow charging can their lifespan be prolonged."

The truth is that fast charging itself does not damage the battery; high temperature is the real culprit. A reasonably designed fast charging technology can take into account both speed and lifespan.

The charging speed of lithium batteries is determined by the "charging current". Fast charging (such as 67W, 120W) essentially shortens the charging time by increasing the current. According to the charge-discharge curve of lithium batteries, the migration rate of lithium ions is relatively fast in the early stage (0%-80% of the battery capacity), and high-current charging does not significantly affect the structure. However, in the later stage (80%-100%), the current needs to be reduced to prevent the accumulation of lithium ions (lithium plating).

At present, the fast charging solutions of mainstream manufacturers (such as Huawei‘s SuperCharge and CATL‘s CTP technology) all adopt a "multi-stage charging strategy" : in the early stage, high current is used for rapid energy replenishment, and in the later stage, it automatically switches to low current slow charging, minimizing damage to the battery to the greatest extent. Experiments show that the cycle life (capacity retention rate after 500 charge and discharge cycles) of lithium batteries using the original factory fast charging heads is almost the same as that of slow charging (about 85% vs 86%).

What really damages the battery is the temperature rise (> 45℃) caused by the heat generated by the resistor during fast charging. Only when non-original fast charging heads (with high internal resistance and high heat generation) are used, or when playing large-scale games while charging (with both the battery and the processor heating up simultaneously), will the battery aging be accelerated.

Misconception 4: "Lithium batteries‘ stop working ‘at low temperatures. Put them in your pocket to warm up before recharging."

The truth is that low temperatures will temporarily suppress the performance of lithium batteries, but they will not cause permanent damage. Heating up while charging may instead cause danger.

The chemical reaction rate of lithium batteries is closely related to temperature: At low temperatures (< 0℃), the migration speed of lithium ions in the electrolyte slows down, and the intercalation ability of the negative electrode decreases, resulting in a reduction in the battery‘s "available capacity" (for example, the capacity at -10℃ is only 70% of that at 25℃), and at the same time, the internal resistance increases, which may lead to "inability to charge" or "power loss anxiety".

However, the impact of low temperatures on lithium batteries is reversible: when the temperature rises above 25℃, the capacity will gradually recover. What really needs attention is:

Avoid charging at low temperatures: When charging at low temperatures, lithium ions may not be fully embedded in the negative electrode, and metallic lithium (" lithium dendrites ") may directly precipitate on the surface of the negative electrode, piercing the separator and causing a short circuit risk.

Avoid using at high temperatures: High temperatures (> 55℃) will accelerate the decomposition of the electrolyte, causing the battery to bulge or even catch fire.

The correct approach: When using lithium battery devices (such as mobile phones and cameras) outdoors in winter, try to keep them close to the skin as much as possible to reduce temperature loss. If charging is needed, first place the device back indoors to warm it up to above 10℃ before charging.

Misconception 5: "New lithium batteries need to be ‘activated‘, and the first three charges should last for 12 hours."

The truth is that "activation" is the "old almanac" of nickel-cadmium batteries. Lithium batteries are activated at the factory and no additional operation is required.

Early nickel-cadmium batteries, due to manufacturing process limitations, might have an oxide layer on the electrode surface and needed to activate capacity through "deep charging and discharging". However, the manufacturing process of lithium batteries is highly mature. The electrode materials have been activated before leaving the factory, and they can be directly charged when used for the first time.

The claim that "the first three charges last for 12 hours" stems from a misunderstanding of nickel-cadmium batteries. Experiments show that no matter how long the lithium battery is charged for the first time (2 hours or 12 hours), there is no difference in its initial capacity. Overcharging may instead accelerate the decomposition of the electrolyte due to a long period of full charge.

The "memory effect" of lithium batteries has long been disproved. Those "maintenance secrets" that have been passed down for many years are mostly the cognitive inertia of the nickel-cadmium battery era or misunderstandings about technical details. Understanding the chemical logic of lithium batteries (the migration laws of lithium ions and the tolerance boundaries of materials) is more important than blindly following "old experience".