Li-ion can be fast charged from 5°C to 45°C (41 to 113°F). Below 5°C, the charge current should be reduced, and no charging is permitted at freezing temperatures because of the reduced diffusion rates on the anode. During charge, the internal cell resistance causes a slight temperature rise that compensates for some of the cold. The internal resistance of all batteries rises when cold, prolonging charge times noticeably. This also affects discharge performance noticeably with Li-ion.
Many battery users are unaware that consumer-grade lithium-ion batteries cannot be charged below 0°C (32°F). Although the pack appears to be charging normally, plating of metallic lithium occurs on the anode during a sub-freezing charge that leads to a permanent degradation in performance and safety. Batteries with lithium plating are more vulnerable to failure if exposed to vibration or other stressful conditions. Advanced chargers (Cadex) prevent charging Li-ion below freezing.
Advancements are being made to charge Li-ion below freezing temperatures. Charging is indeed possible with most lithium-ion cells but only at very low currents. According to research papers, the allowable charge rate at –30°C (–22°F) is 0.02C. At this low current, the charge time would stretch to over 50 hours, a time that is deemed impractical. There are, however, specialty Li-ions that can charge down to –10°C (14°F) at a reduced rate.
Some Li-ion manufacturers offer custom-made cells for cold-charging. Specialty chargers will also be needed that decrease the C-rate according to temperature and charge the battery to a lower voltage peak; 4.00V/cell rather than the customary 4.20V/cell for example. Such limitations decrease the energy a Li-ion battery can hold to roughly 80% instead of the customary 100%. Charge times will also be prolonged and can last 12 hours and longer when cold.
Li-ion batteries charging below 0°C (32°F) must undergo regulatory issue to certify that no lithium plating will occur. In addition, a specially designed charger will keep the allotted current and voltage within a safe limit throughout the temperature bandwidth. Certification of such batteries and chargers are very costly that will reflect in the price. Similar regulatory requirements also apply to intrinsically safe batteries (See BU-304: Why Are Protection Circuits Needed?
There are cell and charger manufacturers claiming to charge Li-ion at low temperatures; however, most companies do not want to take the risk of potential failure and assume liability. Yes, Li-ion will charge at low temperature but research labs dissecting these batteries see concerning results.