Why do lithium batteries require higher temperatures to charge than to discharge?
Lithium batteries exhibit a wider temperature range for discharge (-20°C to 60°C) compared to charging (0°C to 45°C), a fact commonly noted in lithium battery data sheets across various brands and models. This prompts the question: Why do lithium batteries necessitate higher temperatures during charging?
The rationale lies in the phenomenon of “lithium plating,” which occurs at temperatures below 0°C during the charging process. This is primarily attributed to diminished molecular mobility under low-temperature conditions. Notably, lithium-ion in graphite is inhibited, resulting in a decrease in the intercalation rate and a lithium plating reaction on the graphite surface. Consequently, this process elevates internal resistance and results in capacity loss within the lithium battery.
To grasp the chemistry underlying the lithium plating reaction, understanding the operational mechanism of lithium batteries is imperative. These batteries store and discharge energy by facilitating the migration of lithium ions between positive and negative electrodes. During charging, lithium ions exit the positive electrode lattice, traverse the electrolyte separator to the negative electrode, and embed themselves between graphite layers. Conversely, during discharge, lithium ions exit the graphite layers and return to the positive electrode lattice via the electrolyte separator.
However, in low-temperature environments, this process is significantly impeded. Charging lithium batteries below freezing point curtails molecular mobility, thereby decelerating the reaction and material transport processes, especially regarding lithium ion transmission between graphite layers. This impediment results in most lithium ions failing to embed within the graphite layer, instead acquiring electrons on the graphite surface to form metallic lithium. Subsequent accumulation of metallic lithium leads to the formation of dendrites, which can breach the separator between positive and negative electrodes, thereby damaging the battery.
Additionally, discharging a lithium battery below freezing point causes voltage drop due to temperature influence, hastening the battery’s descent to discharge cut-off voltage, thereby reducing low-temperature discharge capacity compared to normal temperature capacity. Nonetheless, this loss is mitigated with subsequent charge and discharge cycles, constituting a reversible loss automatically offset by usage. Conversely, low-temperature charging can cause irreversible dendrite formation and irreversible capacity loss, thereby jeopardizing battery safety.
To ensure the safe use of lithium batteries, charging temperature will be higher.. This facilitates faster ion migration, enhances charging efficiency, and ensures safety. This temperature range is calibrated to strike a balance between performance and reliability. By comprehending these principles, users can optimize the utilization and maintenance of lithium batteries for prolonged performance and longevity.
Despite the challenges posed by low-temperature environments, viable solutions exist. PLB‘s technical experts have found a solution, such as low-temperature preheating for lithium batteries (incorporating intelligent Battery Management Systems and automated heating elements control), have substantially enhanced charge and discharge performance in such conditions.
As a reputable lithium battery manufacturer, PLB offers 26650 cylindrical lifepo4 cells and battery packs globally. Our offerings include personalized customization services encompassing battery cells, structures, and BMS, tailored to meet diverse integration needs. We provide comprehensive and optimal battery customization solutions to our esteemed clientele.