Uncontrollable dendrite growth and low Coulombic efficiency are the two main obstacles that hinder the application of rechargeable Li metal batteries. Here, an optimized amount of potassium hexafluorophosphate (KPF₆, 0.01 M) has been added into the 2 M LiTFSI/ether-based electrolyte to improve the cycling stability of lithium–sulfur (Li–S) batteries. Due to the synergistic effect of self-healing electrostatic shield effect from K⁺ cations and the LiF-rich solid electrolyte interphases derived from PF₆^– anions, the KPF₆ additive enables a high Li Coulombic efficiency of 98.8% (1 mA cm^–2 of 1 mAh cm^–2). The symmetrical Li cell can achieve a stable cycling performance for over 200 cycles under a high Li utilization up to 33.3%. Meanwhile, the polysulfide shuttle has been restrained due to the higher concentration of the LiTFSI in the electrolyte. As a result, the assembled Li–S full cell displays excellent capacity retention with only 0.25% decay per cycle in the final electrolyte. Our work offers a smart approach to improve both the anode and cathode performance by the electrolyte modification of rechargeable Li–S batteries.

中文翻译：

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六氟磷酸钾添加剂可实现稳定的锂硫电池

不可控的枝晶生长和低库仑效率是阻碍可再充电锂金属电池应用的两个主要障碍。这里，六氟磷酸钾（KPF优化的量₆，0.01M）已经被加入到2M的的LiTFSI /醚系电解液，以改善的锂-硫（LI-S）的电池循环稳定性。由于来自K个自愈静电屏蔽效果的协同效应⁺阳离子，以及由PF衍生该LiF富含固体电解质相间₆ ^-阴离子时，KPF ₆添加剂使98.8％（1毫安cm的高锂库仑效率^-2 1 mAh cm ^–2）。在高达33.3％的高Li利用率下，对称Li电池可实现200多个循环的稳定循环性能。同时，由于电解质中LiTFSI的浓度较高，多硫化物的穿梭受到了限制。结果，组装好的Li-S全电池显示出极好的容量保持率，最终电解液中每个循环仅衰减0.25％。我们的工作提供了一种聪明的方法，通过对可充电Li-S电池进行电解质改性来改善阳极和阴极性能。