摘要
The investigation on the cathode material of potassium ion batteries(PIBs),one of the most promising alternatives to lithium ion batteries,is of great significance.Potassium vanadium fluorophosphate(KVPO4F)with a high working voltage is an appealing cathode candidate for PIBs,while the poor cycling performance and low electronic conductivity dramatically hinder the application.Herein,a plum pudding model inspired three-dimensional amorphous carbon network modified KVPO4F composite(KVPO4F@3DC)is successfully designed in this study to tackle these problems.In the composite,KVPO4F particles are homogeneously wrapped by a layer of amorphous carbon and bridged by crosslinked large area carbon sheets.As the cathode for PIBs,the KVPO4F@3DC composite exhibits a high average operating voltage about 4.10 V with a super-high discharge capacity of 102.96 mAh g^-1 at 20 mA g^-1.An excellent long cycle stability with a capacity retention of 85.4%over 550 cycles at 500 mA g^-1 is achieved.In addition,it maintains 83.6%of its initial capacity at 50 mA g^-1 after 100 cycles at 55℃.The design of KVPO4F@3DC with plum pudding structure provides facilitative electron conductive network and stable electrode/electrode interface for electrode,successfully innovating an ultra-stable and high-performance cathode material for potassium ion batteries.
开发环保、低成本的新型正极材料对钾离子电池的发展具有重要意义.高达4.0V的工作电压,使得氟磷酸钒钾(KVPO4F)成为一种极具吸引力的钾电正极材料.然而,KVPO4F材料低的电子导电性(1.84×10^-5 S m^-1)和不稳定的电极/电解质界面,导致其较差的循环稳定性.本文设计并制备由无定型热解碳层及三维导电碳网络对KVPO4F颗粒进行三维包覆,得到KVPF@3DC复合正极并展现出优异的电化学性能.在20,50和500 mA g^-1电流速率下,其放电比容量分别为102.96、96.01和60.02 mAh g^-1;在500 mA g^-1条件下循环550次后,循环保持率高达83.6%.复合材料中,热解碳层均匀包覆在KVPO4F不规则纳米颗粒表面,而三维导电网络则成功连接不同的KVPO4F颗粒,这种特殊结构充分改善了KVPF@3DC复合材料的电子传导能力,同时提高了循环过程中电极材料的界面稳定性,为超稳定高电压钾离子电池正极的开发提供了思路.
作者
Zhaomeng Liu
Jue Wang
Bingan Lu
刘朝孟;王珏;鲁兵安(School of Physics and Electronics,Hunan University,Changsha 410082,China;College of Chemistry and Chemical Engineering,Central South University,Changsha 410083,China;State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body,Hunan University,Changsha 410082,China;Fujian Strait Research Institute of Industrial Graphene Technologies,Quanzhou 362000,China)
基金
financially supported by the National Natural Science Foundation of China(51672078 and 21473052)
Hunan University State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Independent Research Project(71675004)
Hunan Youth Talents(2016RS3025)。
