High volumetric energy density Li-S batteries enabled by dense sulfur monolith cathodes with ultra-small-sized sulfur immobilizers
High volumetric energy density Li-S batteries enabled by dense sulfur monolith cathodes with ultra-small-sized sulfur immobilizers
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DOI：
10.1016/j.cej.2020.126076
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发表时间：
2020-12-01
影响因子：
15.1
通讯作者：
Li, Yunyong
中科院分区：
文献类型：
--
作者：
Huang, Ying;Wang, Wei;Li, Yunyong
由于体积密度低和许多无效孔，实现用于硫/碳阴极的高体积能量密度锂硫电池（LSB）极具挑战性。本文展示了这种致密的硫整体阴极，具有2067 Wh L-1的高体积能量密度和980 mAh cm(-3)的大体积容量（占阴极总体积），其中硫/TiO2量子点（QDs，-3.6 nm）固定在富氮石墨烯（S/TiO2-QDs/N-G）上，硫阴极致密化至体积密度为1.6 g通过干燥石墨烯杂化水凝胶，其电导率接近270 S m(-1) cm(-3)。如此高的体积容量是所有报道的硫/碳阴极中最好的价值之一。此外，整体式正极具有优异的长期循环稳定性，在0.5 A g(-1)电流下循环500次后，每次循环容量衰减仅为0.06%。更重要的是，在4.2 μL mg(-1)的低电解质/硫比下，硫负载量为5.5 mg cm(-2)的厚而致密的整体式正极在0.1 A g(-1)下表现出4.92 mAh cm(-2)的面积容量。此外，TiO2-QDs（锚定在N-G上）对LSB电化学性能的尺寸效应及其对多硫化物的吸附机制表明，致密整体式正极的放电容量和循环稳定性的显着增强源于超小尺寸TiO2-QDs对多硫化物的强大捕获能力。具有超小尺寸硫固定剂（例如金属氧化物、硫化物或磷化物）的高密度硫阴极为设计高体积能量密度LSB提供了一种新策略，即使在贫电解质条件下也具有出色的长期循环稳定性。
It is extremely challenging to achieve a high-volumetric-energy-density lithium-sulfur batteries (LSBs) for sulfur/carbon cathodes due to their low volumetric density and many invalid pores. Herein, such a dense sulfur monolith cathode with a high volumetric energy density of 2067 Wh L-1 and a large volumetric capacity of 980 mAh cm(-3) (of the total volume of cathode) is demonstrated, where sulfur/TiO2 quantum dots (QDs,-3.6 nm) are anchored on nitrogen-rich graphene (S/TiO2-QDs/N-G) and sulfur cathode is densified to a volumetric density of 1.6 g cm(-3) with a conductivity of similar to 270 S m(-1) by drying the graphene hybrid hydrogel. Such high volumetric capacity is one of the best value in all reported sulfur/carbon cathodes. Besides, the monolith cathode gives a superior long-term cycling stability with only 0.06% capacity decay per cycle for 500 cycles at 0.5 A g(-1). More importantly, under a low electrolyte/sulfur ratio of 4.2 mu L mg(-1), the thick and dense monolith cathode with sulfur loading of 5.5 mg cm(-2) displays an areal capacity of 4.92 mAh cm(-2) at 0.1 A g(-1). Furthermore, the size effect of TiO2-QDs (anchored on N-G) on electrochemical performances of LSBs and its adsorption mechanism for polysulfides demonstrate the significantly enhancement in discharge capacity and cycling stability of dense monolith cathode derives from the strong capture ability of ultra-small-sized TiO2-QDs for polysulfides. The highly dense sulfur cathode with ultra-small sized sulfur immobilizers (e.g. metal oxides, sulfides, or phosphides) provides a new strategy for designing high-volumetric-energy-density LSBs with superior long-term cycling stability even in lean electrolyte condition.