A research team led by WANG Zhenyang from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences has developed a thick cathode that helps zinc-ion hybrid capacitors maintain high capacity and fast charging performance.
The study was published in Composites Part B: Engineering.
Zinc-ion hybrid capacitors are promising energy-storage devices, but increasing electrode thickness can make it harder for ions and electrons to move through the material. This can slow charging and affect the stability of the device.
In this study, the researchers used a sequential laser-engineering method to create three functional regions within a single porous graphene electrode. Rather than stacking separate layers, the method forms a continuous structure in which different regions perform different roles.
The inner graphene region provides pathways for electron transport, while the middle region contains manganese oxide (MnOx), the main active material for energy storage. The outer region is rich in oxygen, which helps the electrolyte enter the electrode more easily.
With these regions working together, the electrode maintains continuous pathways for both electron and ion transport even at greater thickness.
The resulting thick electrode retained 93.6% of its capacitance after 12,000 charge-discharge cycles. A zinc-ion hybrid capacitor made with the electrode also showed stable energy-storage performance.
The researchers further used simulations and post-cycling analysis to examine the electrode structure. The results suggest that the oxygen-rich outer region improves electrolyte access and may also help reduce the loss of manganese species during cycling.
The study provides a potential approach to designing thick electrodes for zinc-ion hybrid capacitors.
Figure 1. Schematic illustration of the step-wise functionally graded LPG/LPG@MnOx/LPG-O thick electrode. (Image by LI Nian)
Figure 2. Electrochemical performance of the ZHC device assembled using the step-wise functionally graded LPG/LPG@MnOx/LPG-O thick electrode. (Image by LI Nian)
