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Mr. Kai Zhu and Mr. Dengxue Cao and their team at Harbin Engineering University have recently published a new article on Joule heating, which focuses on the preparation of highly defective graphene by flash Joule heating technique and investigates its application in lithium-ion batteries - the study of high-capacity lithium anode materials based on defect design, and in-depth discussion of its energy storage mechanism, and get the conclusion that this graphene has ultra-high lithium ion storage capacity. This article provides a new perspective for the application of graphene in lithium-ion batteries.
Graphene oxide (GO) is one of the best precursors for defect engineering and doping. In this article, graphene oxide was flash-treated by Joule-heated flashing to remove complex functional groups and introduce a large number of defects, and highly defect-reduced graphene oxide was prepared within 1 ms.
Innovative preparation technology:
Highly defective reduced graphene oxide (F-rGO) was prepared in less than 1 ms (620 microseconds) by Joule thermal flash evaporation.
High Defect Density:
The FJH technology can produce a high density of defects in the graphene lattice, which is conducive to boosting lithium-ion storage capacity.
The enlarged edges of F-rGO show a clear multilayer structure, with some edges showing curled, interconnected carbon nanostructures. In addition, multiple holes appear on the surface, indicating rough surface undulations, which are usually caused by lamellar surface defects.
The multiple concentric rings observed in the SEAD diagram are the result of stacking or folding of carbon layers. Notably, there are several sets of six-fold symmetric bright spots on the rings, which are rotated relative to each other. These bright spots represent atypical Bénard (AB) stacking of the F-rGO layers, caused by small-angle rotations between multiple planes or bending of the graphene edges.
Ultra-high capacity:
The material realizes an ultra-high storage capacity of up to 2500mAh/g, which is significantly better than existing graphene-based anode materials.
Stable and long-lasting performance:
High storage capacity is achieved despite the increasing number of cycles.
The FJH method effectively reduced GO and drastically lowered the oxygen content, resulting in the formation of 3D carbon networks containing a large number of intrinsic defects. The emerging defects during cycling promoted the rise in capacity, which was as high as 2450 mAh/g (1A/g) after 1000 cycles, and was higher than that of graphene synthesized by other methods at different rates. Although the formation of deposited lithium reduces the capacity, the tightly connected 3D network can withstand the volume expansion during anode cycling, with a reversible capacity of 1007 mAh/g after 5000 cycles at a current density of 5 A/g. Although graphene-based lithium batteries still face challenges such as low first discharge efficiency and self-discharge, this preparation method offers a a new approach and provides new insights into understanding the changes in similar thin-layer electrodes during cycling.
Link to paper: https://www.sciencedirect.com/science/article/pii/S1385894723067207
