负离子PF_(6)^(-)对还原解离反应的影响作用机理  

The Effect Mechanism of Anion PF_(6)^(-)on Dissociation Reaction

作　　者：巩颖颖 吴延鸿 尹昊天 周华伟[2] 徐振 GONG Yingying;WU Yanhong;YIN Haotian;ZHOU Huawei;XU Zhen(School of Chemistry and Chemical Engineering,Qilu University of Technology,Jinan 250399,China;School of Chemistry and Chemical Engineering,Liaocheng University,Liaocheng 252059,China)

机构地区：[1]齐鲁工业大学化学与化工学院,山东济南250399 [2]聊城大学化学化工学院,山东聊城252059

出　　处：《聊城大学学报（自然科学版）》2022年第6期51-57,共7页Journal of Liaocheng University:Natural Science Edition

基　　金：国家自然科学基金项目(22073053);山东省自然科学基金项目(ZR2019QB003)资助。

摘　　要：采用密度泛函理论DFT在B3PW91/6-311++G(2df,2p)计算水平下研究了(FEC)Li^(+)(X)(X=PC,PF_(6)^(-),PC-PF_(6)^(-)和PC_(2)-PF_(6)^(-))电解液体系还原分解的微观机理。添加PF_(6)^(-)离子后计算得到的(FEC)Li+(PF_(6)^(-))的还原电位(0.70 V)非常接近实验数值。同时还发现,Li^(+)与PF_(6)^(-)之间的距离从直接接触到被两个溶剂PC分隔,LUMO轨道发生扩散,轨道贡献由18.79%降低到0.12%,并且PF_(6)^(-)对解离反应还原能力的影响逐渐减弱。(FEC)Li^(+)(PF_(6)^(-))解离后Li^(+)与PF_(6)^(-)之间存在静电吸引和范德华力的共同作用,(FEC)Li^(+)(PC)_(2)-PF_(6)^(-)解离后PF_(6)^(-)朝着FEC发生弯曲造成大范围范德华吸引。PF_(6)^(-)位置的不同造成了电解液体系在还原解离过程存在不同的竞争溶剂化结果。To further understand PF_(6)^(-)and different electrolyte systems(FEC)Li^(+)(X)(X=PC,PF_(6)^(-),PC-PF_(6)^(-)and PC_(2)-PF_(6)^(-))on reduction decomposition,the density functional theory(DFT)B3PW91/6-311++G(2df,2p)level was used for comprehensively exploring the electroreduction mechanism.The reduction potential of(FEC)Li+(PF_(6)^(-))is 0.70 V,which is in agreement with experimental reduction peak.As the distance increases from PF_(6)^(-)in direct contact with Li^(+) to the separation of two PC solvent,the LUMO orbital diffuses,the contribution of LUMO orbital decreases from 18.79%to 0.12%,and the effect of reduction capacity becomes weaker and weaker.In addition,it is proved that the interaction between PF_(6)^(-)and Li^(+) is caused by the electrostatic attraction and van der Waals through the analysis of model(FEC)Li^(+)(PF_(6)^(-)).And the bending of PF_(6)^(-)towards FEC arouses wide range of van der Waals attraction on the model of separation(FEC)Li^(+)(PC)_(2)-PF_(6)^(-).The different bonding positions of PF_(6)^(-)lead to different competitive solvation results in the electrolyte system.

关 键 词：氟代碳酸乙烯脂 密度泛函理论 负离子PF-6 还原机理 

分 类 号：O646.1[理学—物理化学]