Both charging and discharging are the mutual conversion of electrical energy and chemical energy. During the movement of positive and negative electrodes, lithium ions are also changing into different compounds.

We can think of lithium ions as a small car with electric charge: when charging, the electric field uses the electric field to drive the car to the negative electrode to store a certain amount of energy (lithium ions are inserted into the micropores of the graphite carbon layer of the negative electrode); when discharging, These charged lithium-ion carts ran to the positive electrode due to a chemical reaction (the deintercalation of lithium ions makes the positive electrode in a lithium-rich state). In this process, a current supply is formed.

In an ideal state, as long as the chemical structure of the positive and negative materials basically does not change, and the reversibility of the battery charge and discharge is very good, the lithium ion battery can guarantee a long-term cycle.

The important thing for fast charging is to ensure that lithium ions are quickly inserted from the positive electrode and quickly inserted into the negative electrode, without causing the deposition of lithium ions.

However, when the current increases, the semi-permeable membrane (SEI membrane) on the surface of the negative electrode (graphite) of the electrode will be broken to a certain extent, causing the electrode material and the electrolyte to react with each other. In addition, the increase in temperature will also cause secondary effects inside the battery. The reaction destroys the chemical substances on the battery, resulting in a decrease in reversibility (that is, the lithium-ion car cannot be driven back and forth), and the battery capacity will continue to decrease.

It’s what we often feel, it’s obviously overflowing with electricity, why the battery is becoming more and more unsustainable.

Take the lithium-ion battery of DJI UAV as an example. A 4480mAh68Wh lithium-ion battery with a voltage of 15.2V only takes 1.5h (compared to iPhone6splus with a battery capacity of 2750mAh and a voltage of 3.8V). Lithium-ion battery life only has 200 cycles. The decline in battery life is obvious.

According to the latest report from DIGITIMES, Apple is also working on upgrading battery charging technology recently, preparing to use 15V to 20V charging equipment to improve battery efficiency and promote new IC technology. However, the equipment supplier of PWMIC also stated that it will bear great risks.

Fast charging protection mode

The three fast charging methods will all have the temperature monitoring method of the battery. What can't be wary of while increasing the voltage is the increase in temperature. If you are using Qualcomm’s QC fast charging technology while playing large-scale games, at this time, due to the chip control, the external voltage is limited to ensure that your phone will not heat up severely, but the charging efficiency will decrease.

For VOOC flash charging, the charging current is controlled in segments, and the charging cable and battery are set in multiple lines. To put it simply, one battery was charged before, but now it is divided into several batteries and charged separately.

In terms of safety, because fast charging has a handshake protocol, the output voltage and current will be coordinated before charging.

Li-ion battery charging is divided into three parts: constant current pre-charge (CCPre-charge), high current constant current charge (CCFastCharge) and constant voltage charge (CV).

The voltage drops after the mobile phone is exhausted. When it is lower than a certain value, the charger will use a relatively low current to precharge the lithium-ion battery. After a period of time, after the voltage of the lithium-ion battery is higher than the predetermined value, it enters the second stage of high-current constant-current charging. At this time, appropriately increasing the current can speed up the charging speed.

If you are using a non-fast-charge mobile phone, the fast-charge charging head will not output high voltage and burn your mobile phone. Just like when you use the iPad charging head to charge the iPhone, the iPad will automatically recognize and input 1A instead of the original 2A.

From the perspective of numerous protection measures, the charging voltage and current of fast charging are in a safe state. As long as the original mobile phone charging adapter is used, it will not bring safety risks.

Even if the batteries equipped on some fast-charging mobile phones have improved cell materials and design, which can realize the rapid insertion and insertion of lithium ions in the battery, the large voltage and current still cause the loss of the battery.

But if you are used to changing a mobile phone in one or two years, or are willing to change a new battery, the impact will be minimal for you.