基于钴酸锂载体构筑高体积比容量硫基复合材料  

LiCoO as Sulfur Host to Enhance Cathode Volumetric Capacity for Lithium-Sulfur Battery

作　　者：王璐[1] 高学平[1] WANG Lu;GAO Xue-ping(Institute of New Energy Material Chemistry,Nankai University,Tianjin 300350,China)

机构地区：[1]南开大学新能源材料化学研究所,天津300350

出　　处：《电化学》2020年第5期750-758,共9页Journal of Electrochemistry

基　　金：国家自然科学基金项目(No.21935006)资助。

摘　　要：锂-硫电池具有高的理论质量/体积能量密度,因而成为最具发展潜力的高比能二次电池体系.然而,由于硫载体通常采用轻质的碳纳米材料,导致硫基复合材料的振实密度和体积比容量均偏低,制约了电池体积能量密度的提升.本文尝试采用具有高密度特征的钴酸锂(LiCoO2)作为硫的载体材料,以构筑高振实密度的硫基复合材料,进而提高硫正极的体积比容量.研究显示,LiCoO2对可溶性多硫化物具有较强的吸附作用,能够促进硫的电化学转化,因而提高了硫的活性物质利用率和循环稳定性.同时,由于具有高的振实密度(1.90 g·cm-3),S/LiCoO2复合材料的首周体积比容量高达1750.5 mAh·cm-3,是常规硫/碳复合材料的2.2倍.因此,本文利用具有高密度特征的LiCoO2作为硫载体来提升硫复合材料的体积比容量,有助于实现锂-硫电池的高体积能量密度.Lithium-sulfur battery is one of the most promising secondary battery systems due to its super high theoretical gravimetric and volumetric energy densities (2600 Wh·kg-1and 2800 Wh·L-1,respectively).However,the practical volumetric capacity of sulfur cathode is still unsatisfied due to the overuse of low-density host materials,such as carbon nanomaterials.Herein,commercial LiCoO2 with the high tap density of 2.94 g·cm-3was used as the host material to build high density sulfur-based composite and compact electrode for increasing the volumetric capacity.Obviously,the tap density of the as-prepared S/LiCoO2 composite was 1.90 g·cm-3,larger than that of the conventional S/carbon composite (0.89 g·cm-3).Correspondingly,the pressed electrode density could be increased to 2.60 g·cm-3by using the S/LiCoO2 composite.In particular,LiCoO2 showed an effective adsorption and electrocatalytic conversion toward soluble intermediate polysulfides,and facilitied to achieve the high utilization of sulfur and cycle stability.As expected,the S/LiCoO2 composite exhibited larger capacity and slower capacity decay rate at 0.1 C rate as compared with the S/carbon composite.Meanwhile,the polarization in discharge-charge processes was smaller for the S/LiCoO2 composite,showing the enhanced reaction kinetics by adopting LiCoO2 host.Therefore,the S/LiCoO2 composite showed superior rate capability and cycle performance at large current density.By virtue of the high tap density,the S/LiCoO2 composite delivered a larger volumetric capacity (1750.5 mAh·cm-3-composite),almost 2.2 times of the S/carbon composite (811.4 m Ah·cm-3-composite).Furthermore,the volumetric capacity of the pressed S/LiCoO2 electrode could reach 1676.8 mAh·cm-3-electrode based on the electrode level,almost 2.5 times of the S/carbon electrode (676.5 m Ah·cm-3-electrode).This work provides a feasible strategy to achieve the high volumetric capacity and energy density of cathode based on LiCoO2 as sulfur host,which provides reference for further developing high vol

关 键 词：锂-硫电池 硫正极 金属氧化物 体积比容量 

分 类 号：O646[理学—物理化学]