With the increasing adoption of electric vehicles, power batteries have become more widely used. However, a major challenge for lithium-ion batteries is the significant reduction in driving range during winter, which is closely related to their inherent properties. At low temperatures, lithium-ion batteries experience poor kinetic performance, leading to reduced capacity, slower charge rates, and overall diminished efficiency. This issue is particularly severe in cold northern winters, where heating systems are typically added to battery packs to maintain performance. Unfortunately, traditional heating methods are inefficient, often requiring tens of minutes to warm up the battery, which greatly reduces the convenience of using electric vehicles. As a result, thermal management of lithium-ion batteries at low temperatures has become a critical concern in battery design.
Recently, Guangsheng Zhang from the University of Pennsylvania proposed an innovative thermal management strategy based on internal heating of lithium-ion batteries. This method enables the battery to quickly return to normal operating temperature, restoring its performance within just 112 seconds at -40°C. The technology also significantly enhances the vehicle’s range—increasing it by 49% at such extreme temperatures.
The core of this technology involves a self-heating battery design. Inside the battery, two nickel sheets are placed at 1/4 and 3/4 of the battery's thickness, each with an impedance of 78mΩ. These sheets are connected in parallel and linked to the battery’s positive and negative terminals through a switch that controls whether the battery is heated. Based on this design, Guangsheng Zhang developed a control scheme that activates the heating system according to the vehicle’s load conditions.
During braking, electric vehicles typically recover energy, which is stored in the battery when the temperature is sufficient. However, at low temperatures, this energy is often wasted because the battery cannot accept a charge efficiently, potentially causing lithium plating on the negative electrode. To address this, Zhang designed a low-temperature energy recovery system that uses the self-heating battery’s rapid warming capability. When the battery is cold, the recovered energy is first used to heat the battery until it reaches an optimal temperature, after which it is stored.
Under simulated driving conditions, the current and power parameters of the battery were observed. It was found that while the external discharge current remains constant, the internal current is used to heat the battery during charging or idle periods. The power curve also reflects this behavior, indicating that the management strategy does not interfere with normal vehicle operation. Additionally, the system ensures that all recovered braking energy is fully utilized—first for heating, then for charging.
The temperature and internal resistance data show that the self-heating battery can raise its temperature from -40°C to 10°C in just 112 seconds, with internal resistance dropping rapidly from 125mΩ to 10mΩ. This rapid recovery is crucial for maintaining battery performance in cold weather. For instance, at -10°C, the battery recovers to 10°C in 33 seconds, demonstrating the technology’s effectiveness in real-world conditions.
Comparing the experimental group (with self-heating battery) and the control group (without), the results were striking. The self-heating battery reached 20°C in 112 seconds, while the control battery only warmed up to 0°C after 3000 seconds, failing to recover any braking energy. This highlights the dramatic improvement in energy utilization and driving range provided by the new system.
Energy consumption analysis further confirmed the benefits. The experimental group showed a much higher proportion of usable driving energy compared to the control group. This is due to the rapid temperature rise, which allows for greater energy recovery during braking. As a result, the driving range of the vehicle was significantly improved.
At different temperatures (-30°C, -20°C, -10°C, and 0°C), the self-heating battery could still provide 78%, 80%, 85%, and 90% of the driving energy available at room temperature. Moreover, as battery specific energy increases, the energy required for heating decreases, making the system even more efficient. For example, when the specific energy reaches 300Wh/kg, the heating energy needed at -40°C drops from 8.7% to 4.8%, and the usable driving energy increases from 74% to 85%. With better insulation, this could be pushed even higher, reaching 94%.
In summary, Guangsheng Zhang’s approach leverages the rapid heating capabilities of self-heating batteries combined with an intelligent management strategy. This innovation allows lithium-ion batteries to quickly recover from low temperatures without affecting normal vehicle operation, making electric vehicles more convenient and practical in cold environments. It also enables faster charging and full utilization of regenerative braking energy, significantly boosting the driving range of electric vehicles. Overall, this technology represents a major step forward in improving the usability and performance of electric vehicles in low-temperature conditions.
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