Table of Contents
A lithium battery can lose a significant amount of usable capacity as the temperature drops below freezing.
At −20°C, published test results for conventional lithium-ion cells show that capacity retention can range from roughly 45% to nearly 90%, depending on the cell design and discharge conditions. For example, one study of commercial 18650 cells found 67–88% of rated capacity at −20°C when discharged at 0.2C, while another lithium cobalt oxide cell tested at 1C delivered about 45% of its reference capacity at −20°C. (Journal of Power Sources; Energies)
At −40°C, conventional lithium-ion batteries can perform much worse. In the same commercial 18650 study, cells delivered only 0–30% of rated capacity at 0.2C, with substantial variation between cells. (Journal of Power Sources)
However, specially engineered low-temperature cells can retain considerably more usable capacity. A silicon/NCA pouch cell using a low-temperature electrolyte delivered more than 700 mAh at −40°C, approximately 65% of its capacity measured at 20°C, without external heating. (Electrochimica Acta)
So there is no single answer to “how much capacity does a lithium battery retain at −20°C or −40°C?” The result depends on cell chemistry, electrolyte formulation, electrode design, discharge rate, cutoff voltage, and the way the battery is tested.
How Much Capacity Does a Lithium Battery at −20°C?
For many conventional lithium-ion batteries, −20°C is challenging but still within a potentially usable discharge range.
A well-known study of five commercial 18650 cells found that their discharge capacity at −20°C ranged from 67% to 88% of rated capacity at 0.2C. The researchers also noted that several cells met an approximately 80% low-temperature capacity level under those test conditions. (Journal of Power Sources)
But the result can change substantially with discharge rate and cell construction.
For example, a separate study testing a lithium cobalt oxide battery at 1C discharge measured an average capacity of about 45.2% of its 25°C reference capacity at −20°C. At −40°C, the same cell delivered only about 11.7% of its reference capacity. (Energies)
This difference highlights an important point:
Low-temperature capacity is not a fixed percentage. The test conditions matter.
For a simple example, a 5,000 mAh battery that delivers 60% of its room-temperature capacity under a specified −20°C test condition would provide approximately 3,000 mAh under that test.
That does not necessarily mean the battery has permanently lost 40% of its chemical capacity. Some of the apparent capacity loss is related to the battery’s reduced ability to move lithium ions and maintain sufficient voltage under cold conditions.
How Much Capacity Does a Lithium Battery Retain at −40°C?
At −40°C, the situation becomes much more severe.
In the commercial 18650 study mentioned above, discharge capacity at −40°C ranged from 0% to 30% of rated capacity at 0.2C. The researchers also found that DC impedance could increase by roughly 20 times compared with room temperature for some cells. (Journal of Power Sources)
This explains why a battery that works normally at room temperature may struggle or shut down in an extreme cold environment.
However, −40°C does not mean that useful battery performance is impossible.
In a study of specially designed silicon/NCA pouch cells, researchers used a low-temperature electrolyte and demonstrated more than 700 mAh of discharge capacity at −40°C, corresponding to approximately 65% of the capacity measured at 20°C. The cells were charged and discharged at −40°C without external heating. (Electrochimica Acta)
Other low-temperature battery technologies have also reported significantly better performance than conventional cells. For example, one published battery development study reported approximately 68% capacity retention at −40°C with an optimized electrolyte formulation, compared with about 20% for a conventional formulation under the reported test conditions. (Progress in Nuclear Energy review)
The engineering lesson is clear:
−40°C performance depends heavily on whether the cell was actually designed for low-temperature operation.
Why Does Lithium Battery Capacity Drop in Cold Temperatures?
Several electrochemical processes slow down when temperature falls below 0°C.
1. Electrolyte conductivity decreases
The electrolyte transports lithium ions between the electrodes. At lower temperatures, electrolyte viscosity increases and ionic conductivity decreases, making lithium-ion transport more difficult. Recent reviews identify reduced electrolyte conductivity as one of the major limitations of lithium-ion batteries at sub-zero temperatures. (RSC Advances; Nano-Micro Letters)
2. Lithium-ion diffusion becomes slower
Lithium ions must move through the electrolyte, electrode materials, and interfacial layers during charging and discharging. At low temperatures, these transport processes become slower, limiting how quickly the cell can deliver its stored energy. (RSC Advances)
3. Internal resistance increases
As temperature falls, charge-transfer and interfacial resistance can increase substantially. This causes greater voltage polarization during discharge. In practical terms, the battery may reach its voltage cutoff earlier, leaving part of its theoretical capacity temporarily unavailable. (Journal of Power Sources; Electrochemical Energy Reviews)
4. Lithium plating becomes a concern during charging
Low-temperature operation is not only a discharge problem.
Charging a lithium-ion battery at sub-zero temperatures can promote lithium plating on the anode, which can reduce usable capacity, shorten cycle life, and create safety risks. Recent research continues to identify lithium plating as a major limitation for low-temperature charging. (Journal of Energy Storage, 2026)
This is why a battery may be able to discharge at −20°C or −40°C while having a much more restricted charging temperature range.
What Factors Affect Lithium Battery Performance at Low Temperatures?
Low-temperature performance is determined by more than battery chemistry alone.
Cell Chemistry
Different cathode and anode combinations can behave very differently under cold conditions. Electrode kinetics, lithium-ion diffusion, and interfacial reactions all influence usable capacity.
Electrolyte Formulation
The electrolyte is particularly important because its viscosity and ionic conductivity change significantly at low temperatures. Low-temperature electrolyte engineering is therefore a major research direction for improving sub-zero performance. (Nano-Micro Letters)
Electrode Design
Anode structure, cathode formulation, electrode loading, particle characteristics, and interfacial properties can all affect low-temperature kinetics.
Discharge Rate
A battery may perform reasonably well at 0.2C but lose much more usable capacity at a higher C-rate because increased polarization and resistance make it harder to maintain the required voltage.
Cell Architecture
Pouch, cylindrical, and other cell structures have different thermal and electrical characteristics. For compact electronic products, electrode design and cell geometry must also be considered together with the available installation space.
Can Lithium Batteries Be Used at −20°C or −40°C?
The answer depends on the application and the battery design.
At −20°C, many conventional lithium-ion cells can still provide useful discharge capacity, although the actual performance depends on the load profile and cell specification.
At −40°C, conventional cells may no longer provide enough usable energy or power for demanding applications. In this temperature range, a battery should generally be selected or engineered specifically for low-temperature operation rather than assuming that a standard lithium-ion cell will be sufficient.
Potential applications include:
- Outdoor IoT and sensor equipment
- Drones and UAVs
- Aerospace systems
- Marine and subsea equipment
- Medical devices used in cold environments
- Industrial monitoring equipment
- Remote and extreme-weather electronics
For these applications, engineers need to evaluate not only capacity retention but also power output, voltage stability, charging conditions, cycle life, and physical battery dimensions.
How to Choose a Lithium Battery for −20°C or −40°C Applications
Before selecting a low-temperature battery, define the actual operating conditions of the product.
Start with these parameters:
- Minimum operating temperature
Is the battery expected to reach −20°C, −30°C, −40°C, or lower? - Required discharge current
A battery operating at 0.2C may behave very differently from one required to deliver 1C or higher. - Required runtime
Determine how much usable energy the device needs at the minimum operating temperature. - Charging temperature
Do not assume that the discharge temperature and charging temperature are the same. - Battery dimensions
For compact products, battery geometry can be just as important as nominal capacity. - Thermal management
Determine whether the system uses insulation, active heating, passive thermal control, or no temperature management.
A low-temperature battery therefore should not be specified simply as “a battery that works at −40°C.” The more useful specification is a complete performance profile showing capacity, discharge rate, voltage behavior, charging limits, and test conditions at the target temperature.
Need a Battery for −20°C or −40°C Applications?
Tell us your operating temperature, battery size, capacity, and discharge requirements. Our engineering team can help evaluate a low-temperature battery solution for your application.
Conclusion
At −20°C, a lithium battery may still retain a substantial portion of its rated capacity, but published results show that performance can vary widely with cell design and discharge conditions. At −40°C, the difference between a conventional cell and a battery specifically engineered for low-temperature operation becomes much more significant.
The most important takeaway is simple:
Low-temperature battery performance is an engineering problem, not just a temperature specification.
For applications operating at −20°C or −40°C, the battery should be designed around the actual load, available space, charging conditions, and required usable capacity at the target temperature—not selected solely by its room-temperature capacity rating.
