Graphene effectively activating "dead" water molecules between manganese dioxide layers in potassium-ion battery  

作　　者：Xinhai Wang Wensheng Yang Shengshang Lu Shangshu Peng Tong Guo Quan Xie Qingquan Xiao Yunjun Ruan 

机构地区：[1]Institute of Advanced Optoelectronic Materials and Technology,College of Big Data and Information Engineering,Guizhou University,Guiyang 550025,Guizhou,China

出　　处：《Journal of Energy Chemistry》2024年第6期306-315,I0008,共11页能源化学（英文版）

基　　金：financially supported by the Scientific and Technological Plan Project of Guizhou Province (Grant No. [2021]060);the Industry and Education Combination Innovation Platform of Intelligent Manufacturing and the Graduate Joint Training Base at Guizhou University (Grant No. 2020-520000-83-01-324061);the Guizhou Engineering Research Center for smart services (Grant No. 2203-520102-04-04-298868)。

摘　　要：Aqueous potassium-ion batteries(APIBs),recognized as safe and reliable new energy devices,are considered as one of the alternatives to traditional batteries.Layered MnO_(2),serving as the main cathode,exhibits a lower specific capacity in aqueous electrolytes compared to organic systems and operates through a different reaction mechanism.The application of highly conductive graphene may effectively enhance the capacity of APIBs but could complicate the potassium storage environment.In this study,a MnO_(2) cathode pre-intercalated with K~+ions and grown on graphene(KMO@rGO) was developed using the microwave hydrothermal method for APIBs.KMO@rGO achieved a specific capacity of 90 mA h g^(-1) at a current density of 0.1 A g^(-1),maintaining a capacity retention rate of>90% after 5000 cycles at 5 A g^(-1).In-situ and exsitu characterization techniques revealed the energy-storage mechanism of KMO@rGO:layered MnO_(2)traps a large amount of "dead" water molecules during K~+ions removal.However,the introduction of graphene enables these water molecules to escape during K~+ ions insertion at the cathode.The galvanostatic intermittent titration technique and density functional theory confirmed that KMO@rGO has a higher K~+ions migration rate than MnO_(2).Therefore,the capacity of this cathode depends on the interaction between dead water and K~+ions during the energy-storage reaction.The optimal structural alignment between layered MnO_(2) and graphene allows electrons to easily flow into the external circuit.Rapid charge compensation forces numerous low-solvent K~+ions to displace interlayer dead water,enhancing the capacity.This unique reaction mechanism is unprecedented in other aqueous battery studies.

关 键 词：GRAPHENE K-ion batteries Mn-based layered oxide Water molecules Density functional theory 

分 类 号：TQ127.11[化学工程—无机化工] TM912[电气工程—电力电子与电力传动]