Abstract
SUMMARYAlternating current preheating can effectively heat the cell while preventing lithium deposition. However, its application in real situation is limited by availability of negative electrode impedance and generation of sinusoidal alternating current (SAC). Based on the fact that negative electrode impedance is dominant in full cell impedance at low temperatures, the strategy of replacing the negative electrode impedance with the full cell impedance is proposed. Generating SAC on vehicle is costly, and may not be the most efficient waveshape in preheating the cell. The strategy of substituting SAC using square wave alternating current (SWAC) is further proposed. Based on the former strategy, applicability boundaries of preventing lithium deposition in terms of frequency and maximum permissible current amplitude for SWAC are provided. Its effectiveness is checked using an 18 650 cell. Neither apparent lithium deposition nor life degradation is exhibited after repeated preheating of 600 min. The preheating rate with different current waveshapes are experimentally compared. The SWAC has larger preheating capability and can warm up the cell in shorter time. To further improve the preheating rate, a temperature‐adaptive profile is developed according to the applicability boundaries, successfully preheating an 18 650 cell from −20°C to 6°C in 540 s.
Published Version
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