元素掺杂碳基材料在锂硫电池中的应用

Application of Element⁃Doped Carbonaceous Materials in Lithium⁃Sulfur Batteries

可移动电子设备、电动汽车及站式储能的蓬勃发展对具有高能量密度和长循环寿命的储能体系的开发提出了迫切需求。锂硫电池由于活性物质硫成本低廉并具有高理论能量密度(2600 Wh·kg^(-1)),成为最具希望的下一代可充电电池。但是,硫及其放电产物导电性差以及多硫化物溶解穿梭导致的一系列严重问题制约了锂硫电池的实际应用。碳基材料通常被用作硫载体以改善正极的导电性,然而,非极性碳材料与极性多硫化物的相互作用较弱,对于多硫化物仅起到有限的物理吸附和阻挡作用,穿梭效应所导致的电池容量严重衰减问题难以得到有效改善。通过杂原子如N、S、Co、B等的掺杂可在碳材料上引入极性或化学吸附位点,大大增强了碳材料对于多硫化物的吸附能力,有效改善了电池的循环稳定性,并且由于掺杂改变了碳材料的电子结构,甚至可以提升碳材料的电子导电性,从而提高了活性物质的利用率。本文对锂硫电池中多孔碳、碳纳米管以及石墨烯等碳基材料常用的元素掺杂进行了介绍,其中包括单元素掺杂、双元素掺杂和多元素掺杂,分析了不同掺杂元素对碳基材料性能的影响,并对元素掺杂碳基材料在锂硫电池中的发展前景进行了展望。

The blossoming of mobile electronic devices,plug⁃in electric vehicles and stationary energy storage have triggered the urgent demand for the exploration of the energy storage systems with high energy density and long cycle life.Lithium⁃sulfur battery is regarded as one of the most promising candidates of the next⁃generation rechargeable batteries,since the active substance sulfur is low cost and possesses high theoretical energy density of 2600 Wh·kg^(-1).However,the practical applications of lithium⁃sulfur battery are hindered by a series of severe problems,which are caused by the insulative nature of sulfur and its discharge products,and the dissolution and shuttling of polysulfides.Carbonaceous materials are generally used as sulfur hosts to improve the conductivity of the cathode.Regrettably,due to the weak interaction between non⁃polar carbonaceous materials and polar polysulfides,the carbonaceous materials can inhibit polysulfides only by limited physical adsorption and restrictions,thus the dramatic capacity decline derived from the notorious“shuttling effect”remains insufficiently resolved.Introducing polar or chemical adsorption sites to carbonaceous materials by element doping,such as N,S,Co and B doping,can greatly enhance the adsorption capacity of carbonaceous materials to polysulfides,so as to sufficiently improve the cycling stability of the cell.Moreover,element doping may improve the electronic conductivity of carbonaceous materials by changing their electronic structure,thus effectively increasing the utilization ratio of the active materials.This article reviews the elements doping commonly applied in carbonaceous materials such as porous carbon,carbon nanotubes and graphene for lithium⁃sulfur batteries,wherein single⁃element doping,dual⁃element doping,and multi⁃element doping are introduced separately.The effects of different doping elements on performance of carbonaceous materials are analyzed.And the development direction of element⁃doped carbonaceous materials in lithium⁃sulfur batteries are prospected.