As a core component of transportation electrification, lithium-ion batteries need to address two critical challenges: achieving high energy density and enabling fast charging. However, changes in electrode thickness could result in a trade-off between these two characteristics. Herein, the impact of electrode thickness on the electrochemical performance, thermal behavior, as well as energy and power density of LiNiCoMnO(NCM)/graphite batteries are investigated through mathematical modeling. Underutilization of active materials of the thick electrode is identified as the primary limitation on rate capability, which can be attributed to the slow solid-state diffusion and poor electrolyte transport within the electrode, especially the enlarged concentration gradients in the solid phase and the lithium depletion in the electrolyte phase during high-rate charging. Evolutions of local current density and heat generation rate along the electrode thickness are compared, identifying the underlying mechanism of inducing uneven reaction kinetics inside the battery. The trade-off between the energy and power density as a function of electrode thickness is investigated based on the limitations of charge transfer and mass transport. Furthermore, the rate-limiting factors under various application requirements are elucidated. This study will provide guidance for the electrode design of high-energy-density batteries with fast-charging capabilities.

中文翻译：

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了解厚电极对高能量密度锂离子电池倍率性能的限制


作为交通电气化的核心组成部分，锂离子电池需要解决两个关键挑战：实现高能量密度和实现快速充电。然而，电极厚度的变化可能导致这两个特性之间的权衡。本文通过数学建模研究了电极厚度对LiNiCoMnO(NCM)/石墨电池的电化学性能、热行为以及能量和功率密度的影响。厚电极活性材料的利用不足被认为是倍率性能的主要限制，这可归因于电极内的固态扩散缓慢和电解质传输不良，特别是固相浓度梯度扩大和锂耗尽高倍率充电时处于电解质相。比较了局部电流密度和发热速率沿电极厚度的变化，确定了引起电池内部不均匀反应动力学的潜在机制。基于电荷转移和质量传输的限制，研究了能量和功率密度之间的权衡作为电极厚度的函数。此外，还阐明了各种应用要求下的速率限制因素。这项研究将为具有快速充电能力的高能量密度电池的电极设计提供指导。