18650 Lithium battery cycle life long?

With the promotion of energy conservation and environmental protection, more and more environmentally friendly products have been applied to the market. And in the battery industry, three lithium batteries with many advantages quickly occupy the market, and gradually replace the traditional lead-acid batteries. For traditional batteries, lithium ternary batteries have long life, energy conservation, environmental protection and no pollution, low maintenance costs, complete charging and discharging, light weight, and other advantages.

Three-dimensional lithium battery

What is triple lithium battery?

In nature, lithium is * light, atomic weight * small metal, its atomic weight is 6.94 g/mol, Hey = 0.53 g/cm3. Lithium is chemically active and easily lost electrons are oxidized to Li +, so the standard electrode potential * negative, -3.045 V, electrochemical equivalent * small, 0.26 g/Ah, These characteristics of lithium determine that it is a material with a high specific energy. Lithium ternary batteries refer to lithium secondary batteries that use three transition metal oxides of nickel cobalt manganese as positive electrode materials. It fully integrates the good cyclic performance of lithium cobalt acid, the high specific capacity of lithium nickel acid, and the high security and low cost of lithium manganese acid. Multielement synergistic composite lithium embedded oxides such as nickel cobalt manganese were synthesized by molecular level mixing, doping, coating and surface modification. It is a lithium ion rechargeable battery that has been widely studied and applied at present.

Lithium battery life

The so-called lithium battery life means that after the battery has been in use for a period of time, the capacity attenuation is 70 % of the nominal capacity(room temperature 25 °C, standard atmospheric pressure, and the battery capacity of 0.2 C discharge), which can be considered as the end of life. In the industry, the cycle life is generally calculated by the number of cycles filled with lithium batteries. In the process of use, irreversible electrochemical reactions occur inside the lithium battery, resulting in a decrease in capacity, such as the decomposition of the electrolyte, inactivation of the active material, and the collapse of the positive and negative polar structures, resulting in a decrease in the number of lithium ions embedded and deembedded. Experiments have shown that higher power discharge will lead to faster attenuation of capacity. If the discharge current is low, the battery voltage will be close to the equilibrium voltage and can release more energy.

The theoretical life of ternary lithium batteries is about 800 cycles, which is medium in commercial rechargeable lithium batteries. lithium iron phosphate is about 2,000 times, while lithium titanate is said to reach 10,000 cycles. At present, mainstream battery manufacturers have promised more than 500 times in their three-way core specifications(charged and discharged under standard conditions), but due to consistency problems, the voltage and internal resistance can not be completely the same. Its cycle life is about 400 times. The manufacturer recommends that the SOC use a window of 10 % to 90 %. It is not recommended to carry out deep charging and discharging. Otherwise, it will cause irreversible damage to the positive and negative polar structure of the battery. If it is calculated in shallow charge, the cycle life will be at least 1,000 times. In addition, if lithium batteries are often discharged at high magnification and high temperature, the battery life will drop significantly to less than 200 times.

Lithium batteries have a service life of only two to three years.

Lithium batteries can generally be filled 300-500 times. It is best to perform partial discharge rather than complete discharge of lithium batteries, and to avoid regular complete discharge as much as possible. Once the battery is off the assembly line, the clock starts to move. Lithium batteries have a life span of two to three years, whether you use them or not.

"Lithium battery" is a type of battery that uses lithium metal or lithium alloy as a negative electrode material and uses a non-aqueous electrolyte solution. In 1912, the lithium metal battery was first proposed and studied by GilbertN. Lewis. In the 1970s, M.S. Whittingham proposed and began to study lithium ion batteries. Due to the very lively chemical properties of lithium metals, the processing, preservation, and use of lithium metals require very high environmental requirements. Therefore, lithium batteries have not been used for a long time. With the development of science and technology, lithium batteries have now become the mainstream.

Lithium batteries can be roughly divided into two categories: lithium metal batteries and lithium ion batteries. Lithium-ion batteries do not contain metallic lithium and can be charged. The fifth-generation lithium metal battery of rechargeable batteries was born in 1996, and its safety, specific capacity, self-discharge rate and performance price are better than those of lithium-ion batteries. Due to its own high-tech requirements, companies in only a few countries are now producing this lithium metal battery.

Use of lithium-ion batteries

This part is the focus of this article, we will talk about three points.

1, how to charge the new battery

In the use of lithium batteries, it should be noted that after the battery is placed for a period of time, it enters a dormant state. At this time, the capacity is lower than normal, and the service time is also shortened. But lithium-ion batteries are easy to activate, as long as they go through three or five normal charges

The electric cycle can activate the battery and restore normal capacity. Due to the characteristics of the lithium battery itself, it is determined that it has almost no memory effect. Therefore, the new lithium battery in the user's mobile phone does not require special methods and equipment during the activation process. Not only in theory, but in my own practice, the "natural activation" of charging from the very beginning is best.

For the "activation" of lithium batteries, there are many arguments: The charging time must be more than 12 hours, repeated three times to activate the battery. This "the first three charges should be charged for more than 12 hours" is obviously a continuation of nickel batteries(such as nickel cadmium and nickel hydrogen). So this statement can be said to be misrepresented at the beginning. The charge-discharge characteristics of lithium batteries and nickel batteries are very different, and it can be very clear to everyone. All the serious formal technical information I have consulted emphasizes that overcharge and overdischarge can cause great damage to lithium batteries, especially liquid lithium-ion batteries. Therefore, charging is best done in accordance with standard time and standard methods, especially without overcharging for more than 12 hours. In general, the charging method described in the mobile phone manual is a standard charging method suitable for the mobile phone.

In addition, lithium cell phones or chargers will automatically stop charging after the battery is full, and there is no so-called "trickle-down" charging of nickel-electric chargers that lasts for more than 10 hours. In other words, if your lithium-ion battery is filled, it is also a waste charge on the charger. Neither of us can guarantee that the characteristics of the battery's charging and discharging protection circuit will never change and the quality will be foolproof, so your battery will be on the edge of danger for a long time. This is another reason why we oppose long charging.

In addition, after charging for some mobile phones for a certain period of time, if the charger is not removed, the system will not only stop charging, but will also start the discharges and charges cycle. This may have its own purpose, but it is obviously not good for the life of batteries and cellphones / chargers. At the same time, long charging takes a long time and often needs to be carried out at night. According to the situation of China's power grid, the voltage at night is relatively high and fluctuating in many places. As has been said before, lithium batteries are very delicate, and they are much less resistant to fluctuations in charge and discharge than nickel, and this poses additional risks.

In addition, another aspect that can not be ignored is that lithium batteries are also not suitable for over-discharge, and over-discharge is also very unfavorable to lithium batteries. This leads to the following questions.

2, when should the charging start in normal use

This is often seen in our forum, because the number of charge and discharge is limited, so the power of the cell phone battery should be recharged as much as possible. But I found an experimental table on the charge and discharge cycle of lithium-ion batteries. The data on the cycle life are listed below:

Cycle life(10 % DOD): & GT; 1,000 times.

Cycle life(100 % DOD): & GT; 200 times

At present, the general cycle life of 3.7 V of 18650 can reach 500 to 1,000 times, and the general life of 3.2 V can reach more than 2,000. Of course, the prerequisite is that qualified batteries produced by regular manufacturers, if they are defective or counterfeit batteries, will have a very short life span.

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