Calendar aging of commercial lithium ion batteries under realistic conditions

The burgeoning global adoption of electric mobility, driven by the prevalent use of lithium-ion batteries as a primary power source, underscores the critical need to discern the influential factors affecting battery performance. Notably, Saudi Arabia's harsh climatic conditions, characterized by scorching summer temperatures surging up to 50 °C, present a compelling imperative for the comprehensive investigation of battery behavior in such an environment. This study delves into calendar aging in LIBs employing a rigorous empirical approach. A cohort of 27 commercial NRC18650B cells was subjected to distinct, real-world storage conditions: controlled indoor environments, outdoor storage within shaded enclosures, and exposure to direct sunlight in the open air. Furthermore, exploring the state of charge (SoC) dynamics encompassed three discrete levels—50%, 75%, and 100%. These investigations were conducted within the challenging climate of Saudi Arabia over a span of two harsh summer months when outdoor temperatures soared to 50 °C. A comprehensive array of performance parameters, including self-discharge, state of health (SoH), internal resistance, and coulombic and energy efficiencies, were examined. The results highlight the paramount role of storage temperature in shaping LIB performance, with heightened significance discerned at full charge (SoC = 100%). A maximum decrement of 6% in the SoH, a 6.5% increase in internal resistance, and notable reductions in coulombic and energy efficiencies (2% and 2%, respectively) were recorded under the most challenging storage scenario—cells housed in glass-covered containers, bared to direct sunlight and charged to full capacity. This study advocates the imperative of implementing effective cooling mechanisms to safeguard lithium-ion batteries' longevity and performance under harsh thermal conditions. The contribution of this research lies in its specific focus on the impact of calendar aging within a region marked by extreme temperatures, thereby extending the boundaries of knowledge and offering vital insights for optimizing battery performance in analogous climates.