Performance of 18650 Lithium-Ion Batteries under Different Ambient Temperatures

Guide to the Use and Maintenance of 18650 Lithium - ion Batteries and Battery Packs

In the current era of rapid technological advancements, 18650 lithium-ion batteries have found extensive 

applications in numerous fields, thanks to their merits such as relatively high energy density, long cycle life, 

and low self-discharge rate. They are used in everything from daily items like flashlights and electric toothbrushes 

to large-scale applications including electric vehicles and energy storage systems. However, the ambient temperature 

has a substantial impact on their performance, which calls for significant attention in practical applications.

I.Performance under Low Temperature Conditions

When the ambient temperature is low, the performance of 18650 lithium-ion batteries deteriorates significantly. 

Firstly, in terms of battery capacity, low temperature causes a remarkable increase in the viscosity of the electrolyte, 

which in turn slows down the diffusion speed of lithium ions within it to a great extent. It's as if the lithium ions are trying 

to move through thick syrup, making their migration extremely difficult and resulting in a significant reduction in the 

usable capacity that the battery can deliver. Generally, at a low temperature of minus 20 degrees Celsius, the battery 

capacity may drop to 50% or even lower of that at room temperature. For instance, a 18650 lithium-ion battery with a 

nominal capacity of 3000mAh at room temperature might only have an actual output capacity of around 1500mAh in a 

low-temperature environment. This has a severe impact on the endurance of devices with high endurance requirements, 

such as electric vehicles, leading to a substantial reduction in their driving range and seriously affecting the user experience.

Secondly, low temperature also affects the internal resistance of the battery. The internal resistance of the battery increases as 

the temperature drops. This is because low temperature impairs the conductivity of electrode materials and hinders the ion conduction 

in the electrolyte. The increase in internal resistance means that more energy is dissipated in the form of heat inside the battery 

during the discharging process, generating heat and further exacerbating the deterioration of battery performance. If this heat 

generation cannot be effectively controlled, it may even lead to safety issues like overheating and potential explosions or fires 

of the battery. In some tests conducted in extremely low-temperature environments, it was observed that during the discharging 

of 18650 lithium-ion batteries, the internal temperature rises rapidly due to the increase in internal resistance. If the discharging 

continues, the temperature of the battery casing may exceed the safety threshold, posing a threat to surrounding equipment and

personnel.

Furthermore, the charging and discharging performance of the battery is also severely compromised in a low-temperature environment. 

Regarding charging, low temperature may give rise to the formation of lithium dendrites. Lithium dendrites are dendritic crystal structures 

that form on the negative electrode surface during the battery charging process due to the uneven deposition of lithium ions. The growth of 

lithium dendrites not only consumes lithium ions in the battery, reducing the battery capacity, but also the sharp dendrites may puncture the 

separator, causing a short circuit between the positive and negative electrodes and triggering a serious safety accident. 

During charging at low temperatures, due to the slow diffusion of lithium ions, it is more likely to form a high-concentration area locally on the 

negative electrode, thereby promoting the growth of lithium dendrites. Consequently, most 18650 lithium-ion batteries need to reduce the 

charging current or even prohibit charging in a low-temperature environment to ensure the safety of the battery. For example, some electric 

vehicles will limit the charging power and extend the charging time in a low-temperature environment, which is highly inconvenient for users 

who urgently need to recharge. In terms of discharging, aside from the capacity reduction and energy loss caused by the increase in internal 

resistance mentioned earlier, low temperature also lowers the discharge plateau of the battery. The discharge plateau refers to a relatively stable

voltage range during the battery discharging process. The decrease in the discharge plateau means that the battery can provide a lower working 

voltage under the same discharging current. For some devices with strict voltage requirements, such as the power supply for chips in electronic 

devices, it may cause the device to fail to work properly.

II. Performance under High Temperature Conditions

In contrast to the low-temperature environment, high-temperature environments also pose a series of problems for 18650 lithium-ion batteries. 

In a high-temperature environment, the electrolyte of the battery becomes more active, and its decomposition rate accelerates, which leads to an 

aggravated capacity attenuation of the battery. On the one hand, the decomposition of the electrolyte consumes lithium ions within it, reducing the 

number of lithium ions that can participate in the electrochemical reaction and thus reducing the battery capacity. On the other hand, the gas 

generated by the decomposition of the electrolyte may accumulate inside the battery, resulting in an increase in internal pressure. If the pressure 

exceeds the bearing limit of the battery casing or safety valve, it will cause the battery to bulge or even explode and other safety accidents. 

For example, in some high-temperature environment tests, when the temperature exceeds 60 degrees Celsius, the capacity of 18650 lithium-ion batteries 

will decline noticeably in a short time. After a long period of exposure to high temperatures, the battery capacity may be permanently lost by 20% - 30%.

The impact of high temperature on the internal resistance of the battery cannot be ignored either. Although high temperature slightly enhances 

the ionic conductivity of the electrolyte, it also accelerates the aging and corrosion of electrode materials, leading to an increase in the interfacial 

resistance between the electrode and the electrolyte. Overall, in a high-temperature environment, the internal resistance of the battery first decreases 

and then increases. In the initial stage, as the temperature rises, the ion conduction accelerates, and the internal resistance slightly decreases. 

However, with the prolongation of the high-temperature duration, the deterioration of electrode materials causes the internal resistance to gradually 

increase. Such changes in internal resistance will lead to more severe heat generation during the charging and discharging process of the battery, 

further accelerating the aging and performance attenuation of the battery. In some high-temperature and high-load application scenarios, such as 

when an electric vehicle is driving at high speed or climbing a slope, the internal temperature of the battery will rise rapidly. The heat generation 

problem caused by the increase in internal resistance will make the battery temperature further out of control, severely affecting the service life 

and safety of the battery.

In terms of charging and discharging performance, high temperature significantly increases the self-discharge rate of the battery. Self-discharge 

refers to the phenomenon that the battery consumes electricity by itself due to internal chemical reactions when it is not connected to an external 

circuit. In a high-temperature environment, the chemical reaction rate inside the battery accelerates, and the self-discharge phenomenon is more 

pronounced. This means that even when the device is turned off or not in use, the battery power will drain quickly. For example, at room temperature, 

the monthly self-discharge rate of a 18650 lithium-ion battery may be around 5%, but in a high-temperature environment, it may rise to 15% or even 

higher. In addition, high temperature also affects the charging efficiency and safety of the battery. During charging, high temperature makes the battery 

more prone to overcharging because high temperature reduces the upper limit of the charging voltage of the battery. If the charging system cannot 

adjust the charging parameters in a timely manner, it may lead to overcharging of the battery and trigger a safety accident. At the same time, although 

the discharging performance of the battery may improve slightly in the short term due to the accelerated ion conduction in a high-temperature environment, 

long-term high-temperature discharging will accelerate the aging and damage of the battery and shorten the cycle life of the battery.

III. Performance under Normal Temperature Conditions

The normal temperature environment is the most stable and ideal state for the performance of 18650 lithium-ion batteries. At normal temperature, the viscosity

 of the battery electrolyte is moderate, and the relative diffusion speed of lithium ions within it is fast, enabling them to fully participate in the electrochemical 

reaction, thus ensuring a high capacity utilization rate of the battery. Generally, in a normal temperature environment of around 25 degrees Celsius, 

18650 lithium-ion batteries can achieve more than 90% of their nominal capacity. For example, a battery with a nominal capacity of 3000mAh can 

have an actual usable capacity of more than 2700mAh at normal temperature, which can meet the endurance requirements of most devices.

At normal temperature, the internal resistance of the battery is relatively low and stable, which makes the energy loss inside the battery small during 

the charging and discharging process. In terms of charging, the battery can accept the input of electrical energy with high efficiency, and the heat 

generated during the charging process is relatively small. There is no need for complex heat dissipation measures to ensure the safety and stability 

of charging. In terms of discharging, the battery can provide a stable voltage output, and the discharge plateau is relatively flat, which can provide a 

continuous and stable power supply for the device. For example, in some handheld electronic devices such as smartphones and tablets, 

18650 lithium-ion batteries can ensure the normal operation of the device for a long time at normal temperature without affecting the user 

experience due to voltage fluctuations or rapid power depletion.

At the same time, the cycle life of the battery can also be well guaranteed at normal temperature. During the normal charging and discharging 

process, the electrode materials and electrolyte of the battery can maintain a relatively stable chemical state and will not age and deteriorate too 

quickly due to drastic temperature changes. Generally, the cycle life of 18650 lithium-ion batteries at normal temperature can reach 500 - 1000 times 

or even more. This means that after multiple charging and discharging cycles, the battery can still maintain a certain capacity and performance and 

provide reliable power support for the device.

IV. Measures to Deal with Different Temperature Environments

In view of the significant impact of ambient temperature on the performance of 18650 lithium-ion batteries, corresponding measures need to be taken 

to deal with different temperature environments in practical applications.

In a low-temperature environment, for some portable devices, thermal insulation materials can be used to wrap the battery to reduce the heat exchange 

between the battery and the external low-temperature environment, thereby alleviating the decline in battery performance to a certain extent. For example,

 some outdoor enthusiasts will put a special thermal insulation sleeve on the 18650 battery when using a flashlight in cold weather to extend the usage 

time of the flashlight. For large devices such as electric vehicles, a battery heating system can be equipped. When the battery temperature is too low, the 

heating system starts to raise the battery temperature to a suitable working range and then performs charging or discharging operations. This can not 

only ensure the performance of the battery but also ensure the safety of charging and discharging. In addition, when using the battery in a low-temperature 

environment, large current discharging operations should be minimized as much as possible, such as avoiding rapid acceleration in electric vehicles, to 

reduce the risks caused by the increase in battery internal resistance.

In a high-temperature environment, heat dissipation measures are crucial. For small electronic devices, the heat dissipation structure of the device 

can be optimized, such as adding heat sinks and using materials with good thermal conductivity, to dissipate the heat generated by the battery in a

timely manner. For example, some high-performance laptops will design a large area of heat dissipation fins near the battery module to ensure the 

normal operation of the battery in a high-temperature environment. For large energy storage systems or electric vehicles, active heat dissipation methods 

such as liquid cooling or air cooling can be adopted. The liquid cooling system takes away heat through the circulation of cooling liquid in the2024-11-13 

battery module, and the air cooling system uses a fan to force air flow to reduce the battery temperature. At the same time, when using the battery in a 

high-temperature environment, it is also necessary to reasonably control the charging and discharging current and voltage of the battery to avoid overcharging, 

overdischarging, and long-term high-load operation to reduce the aging and damage of the battery.

Regardless of whether it is a low-temperature or high-temperature environment, it is necessary to monitor the battery temperature in real-time. 

Through temperature sensors and other devices, obtain the battery temperature information in a timely manner, and then adjust the operation strategy 

of the device or start corresponding temperature control measures according to the temperature situation. For example, in the battery management 

system of an electric vehicle, the temperature of each 18650 battery cell will be monitored in real-time. When the temperature exceeds the safety range, 

the system will issue an alarm and take corresponding protection measures, such as reducing the charging power, limiting the discharging current, or 

starting the heat dissipation system.

In conclusion, the performance of 18650 lithium-ion batteries varies significantly under different ambient temperatures. Low-temperature environments 

lead to a reduction in battery capacity, an increase in internal resistance, a deterioration in charging and discharging performance, and an increase in safety risks.

High-temperature environments cause battery capacity attenuation, changes in internal resistance, an increase in self-discharge rate, and a decline in charging and 

discharging efficiency and safety. While the battery performance is the most stable at normal temperature. In practical applications, we must fully understand the 

impact of temperature on battery performance and take effective measures to deal with different temperature environments. Only in this way can we fully utilize 

the advantages of 18650 lithium-ion batteries, ensure the normal operation and safety of devices, extend the battery life, and promote the sustainable development 

of related fields. Only by doing so can we enjoy the convenience brought by 18650 lithium-ion batteries while avoiding various potential problems caused by temperature factors.