Frigid temperatures, especially those below 20° F (-6° C), significantly impact EVs, causing electrochemical reactions in battery cells to slow considerably. The result is decreased energy production, prolonged charging times, and impaired high-rate discharges (Image courtesy of SOPHIE-CARON).
As cold weather season begins to settle in, visions of stalled cars on the snowy roads of some regions are stoking anxiety among drivers of lithium-ion-powered electric vehicles (EVs). Cold weather can reduce vehicle range — by more than 30% in some models — which can hinder greater EV adoption.
To address concerns about the reliability of EVs in frigid temperatures, advances in battery technology, thermal management, and charging infrastructure systems will be critical.
Fortunately, advances in EV battery performance in cold weather are actively being tested across the automotive and defense sectors, including a new class of electrolyte, liquified gas, and lithium-free batteries. The aim is to drive the next wave of EV adoption by addressing common pain points and increasing consumer confidence.
How the cold impacts batteries
When temperatures drop, the chemical reactions within lithium-ion (Li-ion) battery cells slow down, reducing their operational efficiency and increasing the time it takes to charge the battery).
In addition to powering a vehicle drivetrain, energy is pulled from the batteries to heat the interior, diverting power that would otherwise be directed to maintain optimal performance, and transport drivers to their destination.
Therefore, improving the performance, life, and range of EVs starts with battery chemistry. To date, most research has focused on improving the electrode components of a battery — the anode and cathode — but the tradeoffs of achieving peak performance persist.
One innovation uses lithium-titanate nanocrystals instead of carbon as its anode. This lithium-titanate battery, known for its fast-charging capabilities, can perform in lower temperatures but has a lower voltage of 2.4 V compared to 3.7 V in traditional Li-ion battery technologies. This lower voltage reduces energy density, requiring larger, heavier battery packs.
Additionally, silicon-anode and sodium-ion batteries offer potential solutions to current EV battery challenges.
Silicon-anode Li-ion batteries deliver higher energy density than traditional graphite anodes, enabling a longer range and reduced charging times. However, early analysis of silicon (Si) Li-ion batteries suggests that this material has yet to achieve a “sufficient” life cycle of 180,000 km. But silicon, paired with traditional graphite-anode Li-ion batteries, is showing promise with the combined benefits of energy capacity and longevity.
Sodium-ion batteries (SIBs) are a lithium-free option that has been shown to retain a charging capacity of 90% at -4° F (-20° C) and a long life span. However, these batteries have an overall lower energy density than Li-ion, resulting in a shorter driving range. In tests conducted for the Department of Transportation by the U.S. Naval Research Laboratory, SIBs demonstrated lower energy density than Li-ion batteries – with a voltage range from 1.8 to 3.6 V.
The shift to electrolyte
While the majority of research remains focused on the electrode, the composition of another battery component, the electrolyte, may accelerate benefits.
Solid-state batteries (SSBs) employ a sulfide-based electrolyte and have demonstrated improved energy, stability, and range in cold temperatures. However, SSBs require as much as 30% more lithium than traditional Li-ion batteries. They’re costly to produce, with some estimates as high as $800/kWh, compared to the $120/kWh average of conventional Li-ion batteries.
Another electrolyte innovation is liquified gas, or LiGas, replacing conventional liquid electrolytes.
The features of LiGas batteries include:
- Remaining stable in temperatures as low as -76° F (-60° C).
- Demonstrating 96% energy retention at -4° F (-20° C) and 87% at -40° C (-40° C), respectively.
- Supporting higher-density battery cells, allowing them to store more energy and enabling EVs to increase range.
- Offering greater safer than conventional Li-ion cells. In third-party ballistic testing, LiGas Li-ion batteries burned for six seconds, compared to six minutes for conventional liquid electrolyte cells. A shorter burn time means a reduced risk of thermal propagation.
Smarter energy management
Automakers are also researching ways to optimize the driving range of EVs in cold weather through improved thermal management systems and processes.
For example, pre-conditioning the battery is typically performed while a vehicle is connected to a charging system. Warming the battery before the car is driven reduces energy loss and helps maintain range. Upgrading charging stations with built-in heating systems reduces charging time while improving battery performance.
Additionally, active heating systems keep the battery warm while a vehicle is being driven. EVs equipped with heat pumps moderate the internal temperature in the cabin while improving battery performance. One example is Renault’s “water-cooler system,” which circulates water around the battery, allowing it to recover heat from the battery and retain its charge in colder temperatures.
A multi-faceted approach
The solution to achieving optimal battery performance will not be found in a single innovation. Sustainability incentives alone are unlikely to push all drivers into the EV market. Rather, it will take the integration of advanced battery technologies being developed today into the EVs of tomorrow.
Optimizing tradeoffs between range, performance, and costs — particularly in cold weather conditions — can mitigate seasonal challenges, improve energy efficiency, and increase confidence in EVs.
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