磷酸酯基阻燃电解液用于高安全锂硫电池  

Nonflammable phosphate electrolytes for high-safety lithium-sulfur batteries

作　　者：何孟雪 李一涛 刘亚涛 贾永锋 李刚[2] 贾龙[2] 庞全全 HE Mengxue;LI Yitao;LIU Yatao;JIA Yongfeng;LI Gang;JIA Long;PANG Quanquan(School of Materials Science and Engineering,Peking University,Beijing 100871,China;Beijing Aerospace Automatic Control Institute,Beijing 100854,China)

机构地区：[1]北京大学材料科学与工程学院,北京100871 [2]北京航天自动控制研究所,北京100854

出　　处：《工程科学学报》2024年第4期765-774,共10页Chinese Journal of Engineering

基　　金：国家自然科学基金资助项目(22075002,52203347);中国博士后基金资助项目(2021M690001)。

摘　　要：Li–S电池被认为是最有希望的下一代高能量密度二次电池之一,开发高效阻燃电解液对于提升电池安全性极为重要.本文对高浓度磷酸三乙酯(TEP)和磷酸三(2,2,2-三氟乙基)酯(TFP)电解液在锂–硫化聚丙烯腈(Li–PAN/S)电池中的应用展开了深入研究,以同样的锂盐摩尔比和氟代醚稀释梯度,研究了TEP和TFP基局部高浓度电解液对锂金属负极和硫正极稳定性的影响,详细解析了两种溶剂分子在电池循环过程中的界面反应.研究表明,磷酸酯基高浓度电解液在Li–PAN/S电池中展示了较优异的循环稳定性,通过优化TTE的稀释比例,提升了电池的倍率特性.对比基于TEP和TFP的电解液,发现TEP基电解液具有更好的锂沉积/剥离性能,而TFP基电解液在界面生成更多的有机组分,导致不稳定的界面膜.以TEP212为电解液的锂硫电池能够在1C的倍率下稳定循环200圈以上,放电比容量保持在1080.8 mA·h·g-1.Lithium–sulfur battery is cost-effective and has a theoretical specific energy density of up to 2600 W·h·kg-1;moreover,the earth is rich in sulfur resources;therefore,it is considered a promising candidate for next-generation high-energy-density batteries.However,a few obstacles still persist in the process of commercialization,including the insulation of charge and discharge products,huge volume changes,flammable electrolytes,polysulfide“Shuttle Effect”,and unstable lithium metal anode.Among these challenges,safety is a main concern in the process of commercialization.Batteries using sulfurized polyacrylonitrile(PAN/S)as positive electrode active material have substantial advantages in terms of lifespan and a wider selection of electrolytes.As lithium polysulfide dissolution has not been considered,phosphate-based electrolytes can be used in this system because they also have good nonflammable properties.Phosphate-based flame retardants or nonflammable solvents can capture combustion free radicals and have excellent flame retardant effects as main solvents and flame retardant additives.This study explores the application of high-concentration triethyl phosphate(TEP)and tri(2,2,2-trifluoroethyl)phosphate(TFP)electrolytes in Li-PAN/S batteries to improve battery safety for next-generation high-energy-density secondary batteries.We investigate the effect of TEP and TFP-based electrolytes on the stability of lithium metal negative and sulfur positive electrodes as well as interfacial reactions during battery cycling.Charge–discharge and Li deposition/stripping tests were conducted using a high-concentration electrolyte with a molar ratio of 1∶2 between LiFSI and TEP.The results reveal that the electrolyte can achieve a 99.6%S utilization at 0.1 Cand stable Li deposition/stripping performance.However,the high viscosity and limited ionic conductivity of electrolyte limit its battery performance under high-loading electrode and high-rate conditions.By conducting electrochemical tests on TEP and TFP-based el

关 键 词：阻燃电解液 局部高浓度电解液 磷酸酯 锂硫电池 硫化聚丙烯腈 

分 类 号：TM911[电气工程—电力电子与电力传动]