A major breakthrough in the field of nanoporous filtration m
Source:未知Author:admin Addtime:2020-02-03 11:20:51 Click:
Two-dimensional nanomaterials, such as graphene and transition metal sulfides, have many unique physical, chemical, and electrical properties. Compared with bulk materials, two-dimensional nanomaterials have more specific surface area and active sites, and open ion diffusion channels, which make it possible for rapid transport and efficient storage of lithium ions (and alkali metal ions). Nevertheless, the existing permissions in two-dimensional materials still limit their applications in electrochemical energy storage. For example, during electrode processing and assembly, two-dimensional materials will restack and polymerize, resulting in a significant reduction in the electrochemically active area of the material As the ion transmission path becomes longer, the kinetics slows down; in addition, the high specific surface area of the two-dimensional nanomaterials may consume more electrolyte for forming SEI, resulting in unnecessary side reactions. Therefore, building an efficient energy storage device with both high energy density and high rate performance is still a difficult challenge.
In order to solve the above-mentioned problems, the regulation and design of the two-dimensional nanomaterials' pores have made them look completely new in the application of electrochemical energy storage. Compared with two-dimensional nanosheets with smooth surfaces, porous two-dimensional nanomaterials can provide many structural advantages for electrochemical energy storage applications (as shown in the figure): First, porous two-dimensional nanostructures provide a large effective for electrochemical reactions. Surface area and abundant active sites make a significant contribution to increasing specific energy density. Secondly, the two-dimensional nanomaterials of porous channels can ensure the effective infiltration and penetration of the electrolyte on the electrode surface, and promote the rapid charge transfer between the electrode and the electrolyte interface. Third, porous two-dimensional nanomaterials can significantly alleviate the problem of restacking of two-dimensional nanomaterials. The open structure inside can open blocked active surfaces to improve ion storage. Finally, the pore structure in porous two-dimensional nanomaterials helps to alleviate the volume change during the electrochemical process of electrode materials, especially anode materials based on conversion / alloying, thereby giving the porous two-dimensional nanomaterials superior mechanical properties. And improve its structural degradation during the electrochemical charge and discharge cycle.
Mono-atom-thick nano-porous two-dimensional materials are ideal materials for constructing ultra-thin, highly efficient separation membranes. However, the application of two-dimensional materials with thick atomic layers in practical separation research faces two problems: one is how to prepare large-area crack-free nanopore two-dimensional films with excellent mechanical strength and flexibility; Sub-nanometer pores with high density and uniform pore size distribution, realize efficient selective passage of water molecules and effective retention of solute molecules.
This study reported for the first time a large-area graphene nano-sieve / carbon nanotube film with excellent mechanical properties, high water permeability, ion and molecular retention, and excellent anti-pollution properties. This research overcomes the limitations of two-dimensional materials in the field of practical separation, is a key step in pushing two-dimensional materials into practical separation applications, and represents a milestone breakthrough in the development of two-dimensional materials and carbon nanomaterial separation films.