Dai Yan, Zheng Wenji, Li Xiangcun, Liu Anmin, Zhang Wei, Jiang Xiaobin, Wu Xuemei, Tao Jiahao, He Gaohong
State Key Laboratory of Fine Chemicals, Department of Chemical Engineering, Dalian University of Technology, Linggong Road 2#, Dalian 116024, China.
College of Life Science, Dalian Minzu University, Dalian, Liaoning 116600, China.
ACS Appl Mater Interfaces. 2021 Jan 20;13(2):2521-2529. doi: 10.1021/acsami.0c17454. Epub 2021 Jan 11.
To improve the structural design of electrodes and interlayers for practical applications of Li-S batteries, we report two scalable porous CNT@C membranes for high-energy Li-S batteries. The asymmetric CNT@C (1:2) membrane with both dense and macroporous layers can act as an Al-free cathode for current collection and high sulfur loading, while the symmetric CNT@C (1:1) membrane with hierarchically porous networks can be used as an interlayer to trap lithium polysulfides (LiPSs), thus weakening the shuttle effect by strong adsorption of the N atoms toward LiPSs. The doped N sites in carbon membranes are identified as bifunctional active centers that electrocatalytically accelerate the oxidation of LiS and polysulfide conversion. First-principles calculations reveal that the pyridinic and pyrrolic N sites exhibit favorable reactivity for strong adsorption/dissociation of polysulfide species. They lead to greatly reduced energy and kinetic barrier for polysulfide conversion without weakening the polysulfide adsorption on the membrane. Using the synergistic circulation groove with the two membranes, the practical S loading can be tailored from 1.2 to 6.1 mg cm. The Li-S battery can deliver an areal capacity of 4.6 mA h cm (684 mA h g) at 0.2 C even at an ultrahigh S loading of 6.1 mg cm and a lean electrolyte to sulfur ratio of 5.3 μL mg. Our work for scalable membrane fabrication and structural design provides a promising strategy for practical applications of high-energy Li-S batteries.
为了改进锂硫电池实际应用中电极和中间层的结构设计，我们报道了两种用于高能锂硫电池的可扩展多孔碳纳米管@碳膜。具有致密层和大孔层的不对称碳纳米管@碳（1:2）膜可作为无铝阴极用于集流和高硫负载，而具有分级多孔网络的对称碳纳米管@碳（1:1）膜可作为中间层来捕获多硫化锂（LiPSs），从而通过N原子对LiPSs的强吸附减弱穿梭效应。碳膜中的掺杂N位点被确定为双功能活性中心，可电催化加速LiS的氧化和多硫化物转化。第一性原理计算表明，吡啶型和吡咯型N位点对多硫化物物种的强吸附/解离表现出良好的反应活性。它们导致多硫化物转化的能量和动力学势垒大大降低，同时不减弱多硫化物在膜上的吸附。使用带有这两种膜的协同循环槽，实际硫负载量可在1.2至6.1 mg cm之间调整。即使在6.1 mg cm的超高硫负载和5.3 μL mg的贫电解质与硫比下，锂硫电池在0.2 C时仍可提供4.6 mA h cm（684 mA h g）的面积容量。我们在可扩展膜制造和结构设计方面的工作为高能锂硫电池的实际应用提供了一种有前景的策略。
