Li-S batteries exhibit poor rate capability under lean electrolyte conditions required for achieving high practical energy densities. In this contribution, we argue that the rate capability of commercially-viable Li-S batteries is mainly limited by mass transfer rather than charge transfer during discharge. We first present experimental evidence showing that the charge-transfer resistance of Li-S batteries and hence the cathode surface covered by Li2S are proportional to the state-of-charge (SoC) and not to the current, directly contradicting previous theories. We further demonstrate that the observed Li-S behaviors for different discharge rates are qualitatively captured by a zero-dimensional Li-S model with transport-limited reaction currents. This is the first Li-S model to also reproduce the characteristic overshoot in voltage at the beginning of charge, suggesting its cause is the increase in charge transfer resistance brought by Li2S precipitation.

中文翻译：

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什么限制了锂硫电池在放电过程中的倍率能力：电荷转移或质量转移？

Li-S 电池在实现高实际能量密度所需的贫电解质条件下表现出较差的倍率性能。在这个贡献中，我们认为商业上可行的 Li-S 电池的倍率能力主要受质量转移而不是放电过程中的电荷转移的限制。我们首先展示了实验证据，表明 Li-S 电池的电荷转移电阻以及 Li2S 覆盖的阴极表面与荷电状态 (SoC) 成正比，而不是与电流成正比，这与之前的理论直接矛盾。我们进一步证明，观察到的不同放电速率下的 Li-S 行为是由具有输运限制反应电流的零维 Li-S 模型定性捕获的。