Key advancements in lithium-ion battery technology and a strong push for further domestic infrastructure investment in the past several years have led to rapid growth in the American electric vehicle (EV) market. Electric vehicles can now travel longer distances without stopping to charge, and charging stations are more widely available, reducing many consumers’ anxieties about relying on them as their primary mode of transportation.
Still, many challenges persist before widespread adoption is a possibility. One such challenge is the performance of EV batteries in cold weather environments. Charging these batteries at temperatures near or below 0°C can lead to longer charging times, permanently decreased charging capacity, and damage to the long-term health of the battery. Distance range between charges also decreases significantly in such conditions.
Why Cold Weather Causes Poor EV Battery Performance
Most electric vehicles utilize lithium-ion battery technology due to its high power, light weight, and ability to hold a charge for long periods of time while not in use. The basic components of lithium-ion battery cells include the positively charged cathode, the negatively charged anode, and a liquid electrolyte solution that carries the lithium ions back and forth between the two which powers the battery.
During charging, lithium ions travel from the cathode through the liquid electrolyte to absorb into the anode where they are stored until the battery is in use once again. However, cold temperatures cause some of these ions to fail to absorb properly during the charging process. Instead, some will metallize against the surface of the anode in jagged formations called dendrites in a phenomenon known as lithium plating.
The loss of lithium ions to this unintended chemical reaction within the battery cell results in a permanent decrease in charging capacity since there are fewer mobile ions left to power the battery. The dendrites can eventually damage the battery cell’s internal structure to the point where the cell will no longer function at all and even cause safety concerns.
The design solution that electric vehicle manufacturers have devised to combat the cold is battery pack heating systems that warm up the battery cells before charging in cold weather. However, the energy it takes to produce heat draws power from the initial charging of the battery and can slow the process significantly. Distance range expectancy decreases significantly with cold temperatures as well since more power from the battery must be allocated to heating the cabin and battery pack during use.
The energy efficient alternative to traditional battery pack heating systems are flexible heating elements screen printed with Henkel’s line of Positive Temperature Coefficient (PTC) carbon resistor inks, known as the LOCTITE® ECI 8000 E&C series. These conductive inks safely and rapidly heat the battery to its optimal charging and operating temperature range, with options varying from high to low power (105°C to 40°C). Printed electronics offer superior energy efficiency compared to traditional circuitry.
LOCTITE® ECI 8000 E&C series inks are engineered to effectively “switch off” the heat once they reach their intended temperature range by way of an exponential resistance curve that cuts off the electrical current once it reaches a certain threshold. This “self-regulating” nature prevents overheating malfunctions, which is particularly important with respect to lithium-ion batteries due to their unstable nature at high temperatures.
Henkel’s LOCTITE® brand PTC inks can also be used for other electric vehicle heating components such as heated seats, arm rests, center console covers, and floors, as well as external defoggers or snow and ice melting on back-up cameras, side mirrors, and exterior lights. Their advantage in energy efficiency extends distance range capabilities for the battery when utilized for these other applications as well.
The LOCTITE® ECI 8000 E&C series is compatible with other LOCTITE® silver, carbon, and dielectric ink formulations and can be printed on PET, PEN, or PI film substrates. For more info, click here or contact a Tekra representative today!